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 A225328 a(n) = A002426(n)^n, where A002426 is the central trinomial coefficients. 2
 1, 1, 9, 343, 130321, 345025251, 7858047974841, 1447930954097073657, 2255178731296086753063201, 29588424532574699588724679418659, 3308916781795356089160906125431831800049, 3166064605712293355286523525163381509588445189997 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Logarithmic derivative of A168599 (upon ignoring the initial term, a(0), of this sequence). LINKS G. C. Greubel, Table of n, a(n) for n = 0..46 FORMULA L.g.f.: Sum_{n>=1} a(n)*x^n/n = log( Sum_{n>=0} A168599(n)*x^n ). EXAMPLE L.g.f.: L(x) = x + 9*x^2/2 + 343*x^3/3 + 130321*x^4/4 + 345025251*x^5/5 + ... where exponentiation is an integer series: exp(L(x)) = 1 + x + 5*x^2 + 119*x^3 + 32707*x^4 + 69038213*x^5 + 1309743837515*x^6 + ... + A168599(n)*x^n + ... MATHEMATICA a[n_] := If[n < 0, 0, 3^n Hypergeometric2F1[1/2, -n, 1, 4/3]]; Table[a[n]^n, {n, 0, 50}] (* G. C. Greubel, Feb 27 2017 *) PROG (PARI) {a(n)=sum(k=0, n, binomial(n, k)*binomial(k, n-k))^n} for(n=0, 20, print1(a(n), ", ")) CROSSREFS Cf. A168599, A002426. Sequence in context: A110695 A157589 A055601 * A203745 A012812 A266881 Adjacent sequences:  A225325 A225326 A225327 * A225329 A225330 A225331 KEYWORD nonn AUTHOR Paul D. Hanna, Aug 03 2013 STATUS approved

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Last modified December 12 09:36 EST 2019. Contains 329953 sequences. (Running on oeis4.)