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 A097845 Chebyshev polynomials S(n,171) + S(n-1,171) with Diophantine property. 4
 1, 172, 29411, 5029109, 859948228, 147046117879, 25144026209081, 4299481435634972, 735186181467371131, 125712537549484828429, 21496108734780438290228, 3675708881109905462800559 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS (13*a(n))^2 - 173*b(n)^2 = -4 with b(n)=A098244(n) give all positive solutions of this Pell equation. LINKS Indranil Ghosh, Table of n, a(n) for n = 0..446 Tanya Khovanova, Recursive Sequences Index entries for linear recurrences with constant coefficients, signature (171, -1). FORMULA a(n)= S(n, 171) + S(n-1, 171) = S(2*n, sqrt(173)), with S(n, x)=U(n, x/2) Chebyshev's polynomials of the second kind, A049310. S(-1, x)= 0 = U(-1, x). S(n, 171)=A097844(n). a(n)= (-2/13)*I*((-1)^n)*T(2*n+1, 13*I/2) with the imaginary unit I and Chebyshev's polynomials of the first kind. See the T-triangle A053120. G.f.: (1+x)/(1-171*x+x^2). a(n)=171*a(n-1)-a(n-2), n>1 ; a(0)=1, a(1)=172 . - Philippe Deléham, Nov 18 2008 EXAMPLE All positive solutions of Pell equation x^2 - 173*y^2 = -4 are (13=13*1,1), (2236=13*172,170), (382343=13*29411,29069), (65378417=13*5029109,4970629), ... MATHEMATICA LinearRecurrence[{171, -1}, {1, 172}, 20] (* Harvey P. Dale, Feb 27 2012 *) PROG (PARI) Vec((1+x)/(1-171*x+x^2)+O(x^99)) \\ Charles R Greathouse IV, Feb 08 2017 CROSSREFS Sequence in context: A250340 A035828 A259017 * A261530 A246135 A140002 Adjacent sequences:  A097842 A097843 A097844 * A097846 A097847 A097848 KEYWORD nonn,easy AUTHOR Wolfdieter Lang, Sep 10 2004 STATUS approved

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Last modified May 28 04:27 EDT 2017. Contains 287212 sequences.