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 A375489 #12 Aug 18 2024 20:29:17 %S A375489 1,2,8,48,384,384,4608,64512,1032192,18579456,37158912,817496064, %T A375489 19619905536,510117543936,14283291230208,42849873690624, %U A375489 1371195958099968,46620662575398912,1678343852714360832,63777066403145711616,255108265612582846464,10714547155728479551488 %N A375489 Omit the trailing zeros from double factorial of even numbers (A000165). %F A375489 a(n) = A000165(n)/10^A027868(n). %F A375489 a(n) = a(n-1)*(2*n)/10^A122840(2*n) for n > 0. %t A375489 a[n_]:=2^n*n!/10^IntegerExponent[n!,10]; Array[a,22,0] %Y A375489 Cf. A000165, A004154, A005843, A011557, A027868, A122840, A358987. %K A375489 nonn,base,easy %O A375489 0,2 %A A375489 _Stefano Spezia_, Aug 18 2024