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 A323012 a(n) = (1/sqrt(n^2+1)) * T_{2*n+1}(sqrt(n^2+1)) where T_{n}(x) is a Chebyshev polynomial of the first kind. 2
 1, 5, 305, 53353, 18674305, 10928351501, 9616792908241, 11868363584907985, 19553538801258341377, 41456387654578883552149, 109939727677547706703222001, 356521758767660233608385698361, 1387930545993760882531890016305025 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Seiichi Manyama, Table of n, a(n) for n = 0..193 Wikipedia, Chebyshev polynomials. FORMULA a(n) = Sum_{k=0..n} binomial(2*n+1,2*k)*(n^2+1)^(n-k)*n^(2*k). a(n) ~ 2^(2*n) * n^(2*n). - Vaclav Kotesovec, Jan 02 2019 MATHEMATICA Join[{1}, Table[Sum[Binomial[2 n + 1, 2 k] (n^2 + 1)^(n - k) n^(2 k), {k, 0, n}], {n, 20}]] (* Vincenzo Librandi, Jan 03 2019 *) PROG (PARI) {a(n) = sum(k=0, n, binomial(2*n+1, 2*k)*(n^2+1)^(n-k)*n^(2*k))} (MAGMA) [&+[Binomial(2*n+1, 2*k)*(n^2+1)^(n-k)*n^(2*k): k in [0..n]]: n in [0..15]]; // Vincenzo Librandi, Jan 03 2019 CROSSREFS Diagonal of A188647. Sequence in context: A158994 A158996 A042763 * A300425 A300687 A300610 Adjacent sequences:  A323009 A323010 A323011 * A323013 A323014 A323015 KEYWORD nonn AUTHOR Seiichi Manyama, Jan 02 2019 STATUS approved

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Last modified January 17 18:14 EST 2020. Contains 330987 sequences. (Running on oeis4.)