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 A307376 a(n) = 1/n! * Sum_{k=0..n} (2*n+k)!/((n-k)!*k!*2^k). 1

%I

%S 1,5,81,2330,97405,5360607,366432990,29948982492,2849278444155,

%T 309333396512855,37741150862494651,5112458462852223210,

%U 761358344010536141506,123636426598733578925150,21742842987398075489784900,4116720379411455407932693320,834934865669512891440715729125

%N a(n) = 1/n! * Sum_{k=0..n} (2*n+k)!/((n-k)!*k!*2^k).

%H Seiichi Manyama, <a href="/A307376/b307376.txt">Table of n, a(n) for n = 0..313</a>

%F a(n) = (-1)^n * A144505(2*n+1, n).

%F a(n) ~ 3^(3*n + 1/2) * n^(n - 1/2) / (sqrt(Pi) * 2^(n + 1/2) * exp(n - 2/3)). - _Vaclav Kotesovec_, Apr 06 2019

%t Table[Sum[(2*n + k)!/((n - k)!*k!*2^k)/n!, {k, 0, n}], {n, 0, 20}] (* _Vaclav Kotesovec_, Apr 06 2019 *)

%o (PARI) {a(n) = sum(k=0, n, (2*n+k)!/((n-k)!*k!*2^k))/n!}

%Y Cf. A144505.

%K nonn

%O 0,2

%A _Seiichi Manyama_, Apr 06 2019

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Last modified April 1 19:13 EDT 2023. Contains 361695 sequences. (Running on oeis4.)