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 A232205 #17 Jul 20 2020 11:55:53 %S A232205 1,2,4,24,96,960,5760,80640,645120,11612160,116121600,2554675200, %T A232205 30656102400,797058662400,11158821273600,334764638208000, %U A232205 5356234211328000,182111963185152000,3278015337332736000,124564582818643968000,2491291656372879360000,104634249567660933120000,2301953490488540528640000 %N A232205 a(0)=1; thereafter a(n) = n*a(n-1) if n is even, otherwise a(n) = 2*n*a(n-1). %F A232205 a(n) = n!*2^floor((n+1)/2). - _Jon E. Schoenfield_, Nov 24 2013 %p A232205 c:=proc(n) option remember; if n=0 then 1 %p A232205 elif (n mod 2) = 0 then n*c(n-1) else 2*n*c(n-1); fi; end; %p A232205 [seq(c(n),n=0..20)]; %t A232205 nxt[{n_,a_}]:={n+1,If[OddQ[n],a(n+1),2a(n+1)]}; NestList[nxt,{0,1},30][[All,2]] (* _Harvey P. Dale_, Jul 20 2020 *) %Y A232205 Bisections give: A065140 (even part), A122551 (odd part). %K A232205 nonn %O A232205 0,2 %A A232205 _N. J. A. Sloane_, Nov 21 2013 %E A232205 Definition corrected to match terms by _Jon E. Schoenfield_, Nov 24 2013