A138525 a(n) = Sum_{k=0..n} (2*k)!.

1, 3, 27, 747, 41067, 3669867, 482671467, 87660962667, 21010450850667, 6423384156578667, 2439325392333218667, 1126440053169940898667, 621574841786409380258667, 403913035968392044964258667

Offset: 0

Author

Leroy Quet, Mar 23 2008

Keywords

• easy
• nonn

Comments

Last digit is 7 for n > 2. Therefore there is no square in this sequence except 1. - Altug Alkan, Dec 01 2015

Links

• G. C. Greubel, Table of n, a(n) for n = 0..224

Crossrefs

Cf. A138523, A138524.

Partial sums of A010050.

Programs

Maple

A138525:=n->add((2*k)!, k=0..n): seq(A138525(n), n=0..15); # Wesley Ivan Hurt, Dec 01 2015

Mathematica

Table[Sum[(2i)!, {i, 0, n}], {n, 0, 15}] (* Stefan Steinerberger, Mar 25 2008 *)

PARI

a(n) = sum(k=0, n, (2*k)!); \\ Altug Alkan, Dec 01 2015

Extensions

More terms from Stefan Steinerberger and Robert G. Wilson v, Mar 25 2008