A372994 a(n) = n! a(n-1) / a(n-2), where a(0) = 1, a(1) = 2.

1, 2, 4, 12, 72, 720, 7200, 50400, 282240, 2032128, 26127360, 513216000, 9408960000, 114162048000, 1057763266560, 12116197416960, 239661047808000, 7035575500800000, 187950374092800000, 3249661968064512000, 42064875721374105600, 661340826849411072000

Offset

0,2

Links

Table of n, a(n) for n=0..21.

Mathematica

a[0] = 1; a[1] = 2;
a[n_] := a[n] = n! a[n - 1]/a[n - 2];
Table[a[n], {n, 0, 22}]

Crossrefs

Cf. A000142, A372993.

Sequence in context: A013207 A172165 A078919 * A085864 A060935 A141522

Adjacent sequences: A372991 A372992 A372993 * A372995 A372996 A372997

Keyword

nonn

Author

Clark Kimberling, Jul 16 2024

Status

approved