In this study, new matrices which produce the Pell and Pell-Lucas numbers are given. By using these matrices, new identities and relations related to the Pell and Pell-Lucas numbers are obtained.
Integer sequences are one of the most important topics in number theory. In particular, Fibonacci and Pell number sequences are the most interesting and researched. These integer sequences have been used in many applied mathematics fields. It is well known that matrix relations of the sequences have been used in many areas such as coding theory, statistic theory, and computing theory [11, 15]. The authors in [6, 9] examined the Fibonacci and Lucas numbers by matrices. The authors contributed to the literature with new properties of these numbers. In [2, 3], Horadam investigated Pell and Pell-Lucas sequences. These number sequences are in a relationship with some recursive formulations and with the nth power of some 2- dimensional square matrices, these numbers can be obtained like Fibonacci numbers. In [8], Ercolano found the matrices which produce Pell numbers. In [1], Dasdemir compared Pell and Pell-Lucas numbers by using those matrices. In [5], the authors studied the properties of the Pell matrix with linear algebra. In [4], Değer found the relation between Fibonacci numbers and the suborbital graphs with a new matrix that gives even indexed Fibonacci numbers by using that relation. In [13], the authors examined the relationship between suborbital graphs and Pell numbers. Then, they used a new matrix that produces even indexed Pell and Pell-Lucas numbers.
In this study, firstly we give new matrices related to Pell and Pell-Lucas numbers by using matrix properties. We produce new relations with these matrices. Then using the lambda function from [14] and its properties, we give new identities consisting of Pell and Pell-Lucas numbers.
Pell and Pell-Lucas numbers
Pn is the nth Pell number which satisfies the recurrence relation Pn = 2Pn-1 + Pn-2, n ≥ 2 by initial conditions P0 = 0 and P1 = 1. Similarly, Qn is the nth Pell-Lucas number by Qn = 2Qn-1 + Qn-2, n ≥ 2 and initial conditions Q0 = 1, Q1 = 1. Binet-like formulas for Pn and Qn are and , respectively, where , , and n ≥ 2.
For Pell and Pell-Lucas numbers, the following identities are given:
where See [10] for details.
Some new matrices representations of Pell and Pell-Lucas numbers
In this section, we give some new matrices which produce Pell and Pell-Lucas numbers.
Theorem 1.Let Pn is the nth Pell number and Qn is the nth Pell- Lucas number, then we get the following equation as
where and .
Proof. For the proof we use the diagonal matrix of matrix Z. Because we want to write the nth power of matrix Zn with the equation,
Dn = (P-1ZP) n = P-1ZPP-1 ⋯ P-1ZP = P-1ZnP,
where D is the diagonal matrix, P is the matrix whose column i is ith eigenvector. Hence, we get Zn = PDnP-1. Now let us find the eigenvalues and eigenvectors of matrix Z. Then by the equation
we can find the eigenvalues as and the eigenvectors as
When we write matrix P and its inverse P-1. Then,
and
Therefore, we can write the diagonal matrix as Now, we can write the matrix Zn as:
Zn = PDnP-1 =
If we use Binet like formula of Pell and Pell-Lucas numbers as , where and , we get the matrix Zn with Pell and Pell-Lucas numbers.
Theorem 2.Let Pn and Qn are nth Pell and Pell-Lucas numbers, respectively. Then, for ,
where
Proof. For the proof, we can use the mathematical induction method on n. Firstly, we take for odd integers n, the case for n = 1 is true. We suppose that for n = k, the case is true and we should show the case is true for odd integer n = k + 2. So,
where we use recurrence relation for Pell-Lucas numbers. So, the allegation for all odd integers n is valid. For even integers n, the proof can be made similarly.
Matrix application of Pell, Pell-Lucas numbers
In this section by using the matrices Zn and , we obtain new identities and relations of Pell and Pell-Lucas numbers.
Theorem 3.The following identities are valid for ;
Pm+n = Pn-1Pm + Pm+1Pn,
Pm+n = PnPm-1 + Pn+1Pm,
Qm+n = Qn-1Pm + QnPm+1.
Proof. By using the matrix Zn, we write Zm+n as;
Zm+n =
From the matrix properties, if ZmZn = Zm+n, then,
ZmZn =
is obtained, where
x = (-1) m+n [Pn-1Pm-1 + PnPm],
y = (-1) m+n+1 [Pn-1Pm + Pm+1Pn] ,
,
k = (-1) m+n+1 [PnPm-1 + Pn+1Pm]
l = (-1) m+n [PnPm + Pn+1Pm+1].
So, From the equation Zm+n = ZmZn, we get the identities in the theorem.
Theorem 4.The following equalities are provided for ,
P2n2 - P2n+2P2n-2 = 4,
Q2n2 - Q2n+2Q2n-2 = -8,
where Pn and Qn are nth Pell and Pell-Lucas numbers, respectively.
Proof. Firstly, we establish (i), by using mathematical induction on odd n. It is clear that, det (VL) = -23 for n = 1. Let us suppose for n = k. We must show the statement is true for n = k + 2. If we use the multiplicative property of the determinant, we get
For even values of n, the same motivation is used. So, (i) is proven for all To prove identities (ii) and (iii), we can use equations (7) and (i) for even and odd n, respectively.
Theorem 5.The following equalities are provided for ;
4P2m+2n = Q2mQ2n+2 - Q2m-2Q2n,
2P2m+2n = P2mP2n+2 - P2m-2P2n,
2Q2m+2n = Q2mP2n+2 - Q2m-2P2n,
2P2m-2n = P2m-2P2n - P2mP2n-2,
4P2m-2n = Q2m-2Q2n - Q2mQ2n-2,
2Q2m-2n = P2m-2Q2n - P2mQ2n-2 .
Proof. By using equation (7), we can write matrix as
Firstly, we examine for odd values m and n. So, we can write the following matrix as
Now, let us examine for even m and odd n or odd m and even n. So, we get the matrix as
When we compare equation (8) with equation (11), we obtain the following identity,
Now, let us take the inverse of the matrix , then
When we compute the equality , by using same motivation as above, we obtain following identities. For even values m and n, we get
In the case of odd values m and n, we get
Finally, if we take even m odd n or odd m and even n, we obtain
Now, by using the λ-function from [14], some identities which related to Pell and Pell-Lucas numbers are produced.
Theorem 6.If for all n ≥ 1, Pn is the nth Pell number and Qn is the nth Pell- Lucas number, then
Proof. For the proof we use λ- function for matrix Zn. Firstly, let us write function λ (Zn) as
λ (Zn)
So, by using identities (1), (6) and (4), we obtain
For the equation |Zn*| = |Zn| + lλ (Zn), we can find the matrix Zn* by choosing l = (-1) nPn. Then the matrix Zn* is obtained as follows:
Zn* =
By using recurrence relations of Pell, Pell-Lucas numbers and identities (6) and (1), we get |Zn*| = QnQn+1 + (-1) nPn [QnQn+1 - 2PnPn+1] - kPn + kPnPn+1 .
If we write these calculations in the equation |Zn*| = |Zn| + lλ (Zn), then we get QnQn+1 - 2PnPn+1 = (-1) n .
Theorem 7.If for all n ≥ 1, let Pn is the nth Pell number and Qn is the nth Pell- Lucas number, then
Proof. By using λ function for matrix ; firstly for even n, we get
by using identity (2) and , where and
.
The determinant of matrix is and the determinant of matrix is
Therefore, . If we write them in the equation , then we get
.By using identities (2) and (3), that is 2P2n-1Q2n+1 = 2 + P4n.
When we examine for odd n, the same identity is obtained.
References
1.
DasdemirA.On the Pell, Pell-Lucas and modified Pell numbers bymatrix method,–, Applied Mathematical Sciences5(64) (2011), 3173–3181.
2.
HoradamA.F.Applications of modified pell numbers torepresentations, Ulam Quarterly3 (1994), 34–53.
Değer A.H.Vertices of paths of minimal lengths on suborbitalgraphs, 31(4) (2017), 913–923.
5.
KilicE., TasciD.The linear algebra of the Pell matrix, Bolet&n de la Sociedad Matemática Mexicana11(2005).
6.
KökenF., BozkurtD.On Lucas numbers by the matrix method, Hacettepe Journal of Mathematics and Statistics39(2010), 471–475.
7.
SilvesterJ.R.Fibonacci properties by matrix methods, TheMathematical Gazette63(425) (1979), 188–191.
8.
ErcolanoJ.Matrix generator of Pell sequence, FibonacciQuarterly17(1) (1979), 71–77.
9.
KeskinR., Demirtřk B.Some new Fibonacci and Lucasidentities by matrix methods, International Journal of Mathematical Education in Science and Technology41(3) (2010), 379–387.
10.
KoshyT. Pell and Pell-Lucas Numbers with Applications, Springer, New York, 2014.
11.
AiyubM., EsiA., SubramanianN.Poisson Fibonacci binomialmatrix on rough statistical convergence on triple sequences and itsrate, Journal of Intelligent & Fuzzy Systems36(4) (2019), 3439–3445.
12.
TaŞN., UçarS., Yılmaz ÖzgürN. Pell coding and pell decoding methods with some applications, arXiv preprint arXiv:1706.04377, (2017).
13.
AkbabaÜ., DeğerA.H.Relation between matrices and thesuborbital graphs by the special number sequences, TurkishJournal of Mathematics42 (2022), 753–767.
14.
HoggattV.E., BicknellM.Fibonacci matrices and lambdafunction, Fibonacci Quarterly1 (1963), 47–52.
15.
JiangZ., LiJ., ShenN.On explicit determinants of RFPLR and RFPLL circulant matrices involving Pell numbers in information theory, International Conference on Information Computing and Applications, Springer, Berlin, Heidelberg, 2012. pp. 364–370.