A111424 Sum_{i=1..n} (2i)!/i!.

2, 14, 134, 1814, 32054, 697334, 17994614, 536913014, 18180138614, 688622711414, 28847210769014, 1324142261418614, 66088894793898614, 3563385531547818614, 206406590463275178614, 12782685296230371498614, 842817079876858728618614

Offset

1,1

Comments

a(n) = 4 mod 10 for n>1.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..366

Formula

a(n) ~ 2^(2*n+1/2) * n^n / exp(n). - Vaclav Kotesovec, Oct 16 2014

Example

a(3) = 2!/1! + 4!/2! + 6!/3! = 2 + 12 + 120 = 134.

Mathematica

Accumulate[Table[(2i)!/i!, {i, 20}]] (* Harvey P. Dale, Jul 06 2014 *)

Crossrefs

Sequence in context: A144097 A306081 A326886 * A317356 A336182 A224729

Adjacent sequences: A111421 A111422 A111423 * A111425 A111426 A111427

Keyword

nonn

Author

Jon Perry, Nov 13 2005

Status

approved