A123151 a(n) = A000124(n)*a(n-3) for n > 2, otherwise n!.
1, 1, 2, 7, 11, 32, 154, 319, 1184, 7084, 17864, 79328, 559636, 1643488, 8408768, 67715956, 225157856, 1294950272, 11647144432, 43005150496, 273234507392, 2702137508224, 10923308225984, 75685958547584, 813343389975424, 3560998481670784, 26641457408749568
Offset: 0
Links
- G. C. Greubel, Table of n, a(n) for n = 0..500
Programs
-
Magma
function a(n) // a = A123151 if n le 2 then return Factorial(n); else return (n^2+n+2)*a(n-3)/2; end if; end function; [a(n): n in [0..30]]; // G. C. Greubel, Jul 17 2023
-
Mathematica
a[n_]:= a[n]= If[n<3, n!, (1/2)*(n^2+n+2)*a[n-3]]; Table[a[n], {n,0,30}] -
SageMath
@CachedFunction # a = A123151 def a(n): return factorial(n) if (n<3) else (n^2+n+2)*a(n-3)/2 [a(n) for n in (0..30)] # G. C. Greubel, Jul 17 2023
Formula
Extensions
Edited by N. J. A. Sloane, Oct 04 2006
Edited by G. C. Greubel, Jul 17 2023