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 A290046 #8 Jul 24 2017 11:57:52
%S A290046 1,2,46,899,45181,1981844,183812716,13565497859,1948425055741,
%T A290046 11509621621134,42638364069002866,6290021506693847759,
%U A290046 1672053831207666984241,318158932941670103831384,106827312624343125411048616,25266964023001914822246560759
%N A290046 a(n) = |Sum_{k=0..n} (-1)^k*(3k)!!|.
%C A290046 a(26) = 2 * 41 * 121157 * 160215276888781 * 1706504288791033 * 4123576055576581869533. Thus a(n) are multiples of 41 for n >= 26.
%t A290046 Table[Abs@ Sum[(-1)^k*(3 k)!!, {k, 0, n}], {n, 0, 15}] (* _Michael De Vlieger_, Jul 19 2017 *)
%Y A290046 Cf. A006882, A138525.
%K A290046 easy,nonn
%O A290046 0,2
%A A290046 _XU Pingya_, Jul 19 2017