A138525 - OEIS

%I #25 Jun 24 2022 19:59:13

%S 1,3,27,747,41067,3669867,482671467,87660962667,21010450850667,

%T 6423384156578667,2439325392333218667,1126440053169940898667,

%U 621574841786409380258667,403913035968392044964258667

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

%C Last digit is 7 for n > 2. Therefore there is no square in this sequence except 1. - _Altug Alkan_, Dec 01 2015

%H G. C. Greubel, <a href="/A138525/b138525.txt">Table of n, a(n) for n = 0..224</a>

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

%t Table[Sum[(2i)!, {i, 0, n}], {n, 0, 15}] (* _Stefan Steinerberger_, Mar 25 2008 *)

%o (PARI) a(n) = sum(k=0, n, (2*k)!); \\ _Altug Alkan_, Dec 01 2015

%Y Cf. A138523, A138524.

%Y Partial sums of A010050.

%K easy,nonn

%O 0,2

%A _Leroy Quet_, Mar 23 2008

%E More terms from _Stefan Steinerberger_ and _Robert G. Wilson v_, Mar 25 2008