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 A159661 The general form of the recurrences are the a(j), b(j) and n(j) solutions of the 2 equations problem: 11*n(j) + 1 = a(j)*a(j) and 13*n(j) + 1 = b(j)*b(j) with positive integer elements. the solutions of the 2 equations problem: 11*n(j) + 1 = a(j)*a(j); 13*n(j) + 1 = b(j)*b(j); with integer numbers. 3
 1, 25, 599, 14351, 343825, 8237449, 197354951, 4728281375, 113281398049, 2714025271801, 65023325125175, 1557845777732399, 37323275340452401, 894200762393125225, 21423495022094552999, 513269679767876146751, 12297048819406932969025, 294615901985998515109849 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Colin Barker, Table of n, a(n) for n = 1..725 Index entries for linear recurrences with constant coefficients, signature (24,-1). FORMULA The a(j) recurrence is a(1)=1; a(2)=23; a(t+2) = 24*a(t+1) - a(t); resulting in a(j) terms 1, 23, 551, 13201, 316273, 7577351, 181540151, 4349386273. The b(j) recurrence is b(1)=1; b(2)=23; b(t+2) = 24*b(t+1) - b(t); resulting in b(j) terms 1, 25, 599, 14351, 343825, 8237449 as listed above. The n(j) recurrence is n(0)=n(1)=0; n(2)=48; n(t+3) = 575*(n(t+2) - n(t+1)) + n(t) resulting in n(j) terms 0, 0, 48, 27600, 15842400, 9093510048, 5219658925200. From Colin Barker, Sep 25 2015: (Start) a(n) = 24*a(n-1)-a(n-2) for n>2. G.f.: x*(1+x) / (1 - 24*x + x^2). (End) a(n) = (12+sqrt(143))^(-n)*(-11 - sqrt(143) + (-11+sqrt(143))*(12+sqrt(143))^(2*n))/22. - Colin Barker, Jul 26 2016 From G. C. Greubel, Jun 25 2022: (Start) a(n) = ChebyshevU(n-1, 12) + Chebyshev(n-2, 12). E.g.f.: exp(12*x)*(cosh(sqrt(143)*x) + sqrt(13/11)*sinh(sqrt(143)*x)). (End) MAPLE for a from 1 by 2 to 100000 do b:=sqrt((13*a*a-2)/11): if (trunc(b)=b) then n:=(a^2-1)/C: La:=[op(La), a]: Lb:=[op(Lb), b]: Ln:=[op(Ln), n]: endif: enddo: MATHEMATICA LinearRecurrence[{24, -1}, {1, 25}, 31] (* G. C. Greubel, Jun 25 2022 *) PROG (PARI) Vec(x*(x+1)/(x^2-24*x+1) + O(x^20)) \\ Colin Barker, Sep 25 2015 (PARI) a(n) = round((12+sqrt(143))^(-n)*(-11-sqrt(143)+(-11+sqrt(143))*(12+sqrt(143))^(2*n))/22) \\ Colin Barker, Jul 26 2016 (Magma) [n le 2 select 24*n-23 else 24*Self(n-1) -Self(n-2): n in [1..31]]; // G. C. Greubel, Jun 25 2022 (SageMath) [chebyshev_U(n-1, 12) + chebyshev_U(n-2, 12) for n in (1..30)] # G. C. Greubel, Jun 25 2022 CROSSREFS Cf. A077423, A157456. Sequence in context: A239822 A264220 A228827 * A104643 A162811 A163175 Adjacent sequences: A159658 A159659 A159660 * A159662 A159663 A159664 KEYWORD nonn,easy AUTHOR Paul Weisenhorn, Apr 19 2009 STATUS approved

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Last modified June 25 03:44 EDT 2024. Contains 373693 sequences. (Running on oeis4.)