A232205 a(0)=1; thereafter a(n) = n*a(n-1) if n is even, otherwise a(n) = 2*n*a(n-1).

1, 2, 4, 24, 96, 960, 5760, 80640, 645120, 11612160, 116121600, 2554675200, 30656102400, 797058662400, 11158821273600, 334764638208000, 5356234211328000, 182111963185152000, 3278015337332736000, 124564582818643968000, 2491291656372879360000, 104634249567660933120000, 2301953490488540528640000

Offset

0,2

Links

Table of n, a(n) for n=0..22.

Formula

a(n) = n!*2^floor((n+1)/2). - Jon E. Schoenfield, Nov 24 2013

Maple

c:=proc(n) option remember; if n=0 then 1
elif (n mod 2) = 0 then n*c(n-1) else 2*n*c(n-1); fi; end;
[seq(c(n), n=0..20)];

Mathematica

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 *)

Crossrefs

Bisections give: A065140 (even part), A122551 (odd part).

Sequence in context: A192384 A119036 A192382 * A170931 A317999 A371892

Adjacent sequences: A232202 A232203 A232204 * A232206 A232207 A232208

Keyword

nonn

Author

N. J. A. Sloane, Nov 21 2013

Extensions

Definition corrected to match terms by Jon E. Schoenfield, Nov 24 2013

Status

approved