A123150 a(n) = (n^5 - n^4 - n^3 + n^2 - 1)*a(n-5) for n > 4, otherwise n!.

1, 1, 2, 6, 24, 2399, 6299, 28222, 169338, 1244136, 213748501, 914608501, 6392593442, 57693964614, 618160168824, 150820728557099, 895583729570699, 8513087005239262, 102642351647368962, 1446049101566437896, 457348626455818450501, 3475580442134239108501

Offset: 0

Author

Roger L. Bagula, Oct 01 2006

Keywords

• nonn
• easy

Links

• G. C. Greubel, Table of n, a(n) for n = 0..445

Crossrefs

Cf. A123151.

Programs

Magma

function a(n) // a = A123150
  if n le 4 then return Factorial(n);
  else return (n^2*(n-1)*(n^2-1) -1)*a(n-5);
  end if;
end function;
[a(n): n in [0..30]]; // G. C. Greubel, Jul 17 2023

Mathematica

a[n_]:= a[n]= If[n<5, n!, (n^2*(n-1)*(n^2-1) -1)*a[n-5]];
Table[a[n], {n,0,30}]

SageMath

@CachedFunction # a = A123150
def a(n): return factorial(n) if (n<5) else (n^2*(n-1)*(n^2-1) -1)*a(n-5)
[a(n) for n in (0..30)] # G. C. Greubel, Jul 17 2023

Formula

a(n) = n! for n < 5, otherwise a(n) = (n^5 -n^4 -n^3 +n^2 -1)*a(n-5).

Extensions

Edited by N. J. A. Sloane, Oct 04 2006

Edited by G. C. Greubel, Jul 17 2023