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 A097311 Chebyshev polynomials of the second kind, U(n,x), evaluated at x=14. 3
 0, 1, 28, 783, 21896, 612305, 17122644, 478821727, 13389885712, 374437978209, 10470873504140, 292810020137711, 8188209690351768, 228977061309711793, 6403169506981578436, 179059769134174484415, 5007270366249903985184 (list; graph; refs; listen; history; text; internal format)
 OFFSET -1,3 COMMENTS b(n)^2 - 195*a(n)^2 = +1 with b(n):=A097310(n) gives all nonnegative integer solutions of this Pell equation. For positive n, a(n) equals the permanent of the n X n tridiagonal matrix with 28's along the main diagonal, and i's along the superdiagonal and the subdiagonal (i is the imaginary unit). [John M. Campbell, Jul 08 2011] For n>=1, a(n) equals the number of 01-avoiding words of length n-1 on alphabet {0,1,...,27}. - Milan Janjic, Jan 26 2015 LINKS Indranil Ghosh, Table of n, a(n) for n = -1..689 Tanya Khovanova, Recursive Sequences Index entries for linear recurrences with constant coefficients, signature (28, -1) FORMULA a(n) = S(n, 28) = U(n, 14), n>=-1, with Chebyshev polynomials of the second kind. See A049310 for the triangle of S(n, x) coefficients. S(-1, x) := 0 =: U(-1, x). G.f.: 1/(1-28*x+x^2). a(n) = ((14+sqrt(195))^(n+1) - (14-sqrt(195))^(n+1))/(2*sqrt(195)), (Binet form). a(n) = 28*a(n-1)-a(n-2); a(0)=1, a(1)=28; a(-1)=0. - Zerinvary Lajos, Apr 29 2009 a(n) = Sum_{k, 0<=k<=n} A101950(n,k)*27^k. - Philippe Deléham, Feb 10 2012 With an offset of 0, product {n >= 1} (1 + 1/a(n)) = 1/13*(13 + sqrt(195)). - Peter Bala, Dec 23 2012 Product {n >= 2} (1 - 1/a(n)) = 1/28*(13 + sqrt(195)). - Peter Bala, Dec 23 2012 a(n) = sqrt((A097310(n)^2 - 1)/195). MATHEMATICA lst={}; Do[AppendTo[lst, GegenbauerC[n, 1, 14]], {n, 0, 8^2}]; lst (* Vladimir Joseph Stephan Orlovsky, Sep 11 2008 *] LinearRecurrence[{28, -1}, {0, 1}, 17] (* Ray Chandler, Aug 12 2015 *) PROG (Sage) [lucas_number1(n, 28, 1) for n in xrange(0, 20)] # Zerinvary Lajos, Jun 25 2008 CROSSREFS Cf. A049310, A097310. Sequence in context: A158545 A291997 A171333 * A223495 A209228 A208505 Adjacent sequences:  A097308 A097309 A097310 * A097312 A097313 A097314 KEYWORD nonn,easy AUTHOR Wolfdieter Lang, Aug 31 2004 STATUS approved

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Last modified November 11 22:31 EST 2019. Contains 329046 sequences. (Running on oeis4.)