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 A097774 Chebyshev U(n,x) polynomial evaluated at x=393=2*14^2+1. 2
 1, 786, 617795, 485586084, 381670044229, 299992169177910, 235793463303793031, 185333362164612144456, 145671786867921841749385, 114497839144824403002872154, 89995155896045112838415763659 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Used to form integer solutions of Pell equation a^2 - 197*b^2 =-1. See A097775 with A097776. LINKS Tanya Khovanova, Recursive Sequences Index entries for linear recurrences with constant coefficients, signature (786, -1). FORMULA a(n) = 2*393*a(n-1) - a(n-2), n>=1, a(0)=1, a(-1):=0. a(n) = S(n, 2*393)= U(n, 393), Chebyshev's polynomials of the second kind. See A049310. G.f.: 1/(1-2*393*x+x^2). a(n)= sum((-1)^k*binomial(n-k, k)*786^(n-2*k), k=0..floor(n/2)), n>=0. a(n) = ((393+28*sqrt(197))^(n+1) - (393-28*sqrt(197))^(n+1))/(56*sqrt(197)), n>=0. MATHEMATICA LinearRecurrence[{786, -1}, {1, 786}, 30] (* or *) CoefficientList[ Series[ 1/(1-786x+x^2), {x, 0, 30}], x] (* Harvey P. Dale, Jun 15 2011 *) CROSSREFS Sequence in context: A097776 A031526 A108795 * A031896 A045231 A267476 Adjacent sequences:  A097771 A097772 A097773 * A097775 A097776 A097777 KEYWORD nonn,easy AUTHOR Wolfdieter Lang, Aug 31 2004 STATUS approved

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Last modified September 23 23:21 EDT 2018. Contains 315306 sequences. (Running on oeis4.)