A374982 a(n) = (1/3)*Product_{k=0..n} (F(k)+3), where F=A000045 (Fibonacci numbers).

1, 4, 16, 80, 480, 3840, 42240, 675840, 16220160, 600145920, 34808463360, 3202378629120, 470749658480640, 111096919401431040, 42216829372543795200, 25878916405369346457600, 25620127241315652993024000, 40992203586105044788838400000

Offset: 0

Author

Clark Kimberling, Aug 03 2024

Keywords

• nonn

Comments

Trivially, a(n+1)/a(n) is an integer for n>=0, so (a(n)) is a divisibility sequence.

Crossrefs

Cf. A000045, A082480.

Programs

Mathematica

q[n_] := Fibonacci[n]
p[n_] := Product[q[k] + 3, {k, 0, n}]
Table[(1/3)*Simplify[p[n]], {n, 0, 20}]

PARI

a(n) = prod(k=0, n, fibonacci(k)+3)/3; \\ Michel Marcus, Aug 04 2024