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