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 A099397 Chebyshev's polynomial of the first kind, T(n,x), evaluated at x=51. 4
 1, 51, 5201, 530451, 54100801, 5517751251, 562756526801, 57395647982451, 5853793337683201, 597029524795704051, 60891157735824130001, 6210301059529265556051, 633389816914249262587201 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Used in A099374. Numbers n such that 26*(n^2-1) is square. - Vincenzo Librandi, Nov 17 2010 LINKS Indranil Ghosh, Table of n, a(n) for n = 0..497 Tanya Khovanova, Recursive Sequences Index entries for linear recurrences with constant coefficients, signature (102, -1). FORMULA a(n) = 102*a(n-1) - a(n-2), n>=1; a(-1):= 51, a(0)=1. a(n) = T(n, 51) = (S(n, 102)-S(n-2, 102))/2 = S(n, 102)-51*S(n-1, 102) with T(n, x), resp. S(n, x), Chebyshev's polynomials of the first, resp. second, kind. See A053120 and A049310. S(n, 102)=(n). a(n) = (ap^n + am^n)/2 with ap := 51+10*sqrt(26) and am := 51-10*sqrt(26). a(n) = Sum_{k=0..floor(n/2)} (((-1)^k)*(n/(2*(n-k)))*binomial(n-k, k)*(2*51)^(n-2*k)), n >= 1. a(0):=1. G.f.: (1 - 51*x)/(1 - 102*x + x^2). MATHEMATICA LinearRecurrence[{102, -1}, {1, 51}, 13] (* Ray Chandler, Aug 11 2015 *) PROG (MAGMA) [n: n in [1..1000] |IsSquare(26*(n^2-1))] // Vincenzo Librandi, Nov 17 2010 (PARI) a(n) = polchebyshev(n, 1, 51); \\ Michel Marcus, Jan 20 2018 CROSSREFS Row 5 of array A188645. Sequence in context: A172868 A015271 A221116 * A093251 A184282 A232278 Adjacent sequences:  A099394 A099395 A099396 * A099398 A099399 A099400 KEYWORD nonn,easy AUTHOR Wolfdieter Lang, Oct 18 2004 STATUS approved

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Last modified October 16 23:08 EDT 2018. Contains 316275 sequences. (Running on oeis4.)