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A372994
a(n) = n! a(n-1) / a(n-2), where a(0) = 1, a(1) = 2.
1
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
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
Sequence in context: A013207 A172165 A078919 * A085864 A060935 A141522
KEYWORD
nonn
AUTHOR
Clark Kimberling, Jul 16 2024
STATUS
approved