This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A138525 #25 Jun 24 2022 19:59:13
%S A138525 1,3,27,747,41067,3669867,482671467,87660962667,21010450850667,
%T A138525 6423384156578667,2439325392333218667,1126440053169940898667,
%U A138525 621574841786409380258667,403913035968392044964258667
%N A138525 a(n) = Sum_{k=0..n} (2*k)!.
%C A138525 Last digit is 7 for n > 2. Therefore there is no square in this sequence except 1. - _Altug Alkan_, Dec 01 2015
%H A138525 G. C. Greubel, <a href="/A138525/b138525.txt">Table of n, a(n) for n = 0..224</a>
%p A138525 A138525:=n->add((2*k)!, k=0..n): seq(A138525(n), n=0..15); # _Wesley Ivan Hurt_, Dec 01 2015
%t A138525 Table[Sum[(2i)!, {i, 0, n}], {n, 0, 15}] (* _Stefan Steinerberger_, Mar 25 2008 *)
%o A138525 (PARI) a(n) = sum(k=0, n, (2*k)!); \\ _Altug Alkan_, Dec 01 2015
%Y A138525 Cf. A138523, A138524.
%Y A138525 Partial sums of A010050.
%K A138525 easy,nonn
%O A138525 0,2
%A A138525 _Leroy Quet_, Mar 23 2008
%E A138525 More terms from _Stefan Steinerberger_ and _Robert G. Wilson v_, Mar 25 2008