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A109398 a(n) = (1/n!)*Sum_{k=0..n} (n+k)!. 1

%I

%S 1,3,16,145,1926,33649,726328,18636561,553680370,18684924841,

%T 705833193924,29502690532393,1351724235304366,67359683340291105,

%U 3627011494019437936,209846445862386234529,12982402818188717219658

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

%F a(n) ~ 2^(2*n + 1/2) * n^n / exp(n). - _Vaclav Kotesovec_, Nov 27 2017

%t Table[Sum[Binomial[n+k,k]k!,{k,0,n}],{n,0,100}] (* _Emanuele Munarini_, Sep 20 2016 *)

%o (Maxima) makelist(sum(binomial(n+k,k)*k!,k,0,n),n,0,12); // _Emanuele Munarini_, Sep 20 2016 //

%Y Cf. A111686.

%K easy,nonn

%O 0,2

%A _Vladeta Jovovic_, Aug 26 2005

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Last modified January 31 05:18 EST 2023. Contains 359947 sequences. (Running on oeis4.)