login
a(n) = (1/2)*Product_{k=0..n} (F(k)+2), where F=A000045 (Fibonacci numbers).
1

%I #13 Aug 04 2024 20:46:10

%S 1,3,9,36,180,1260,12600,189000,4347000,156492000,8920044000,

%T 811724004000,118511704584000,27850250577240000,10555244968773960000,

%U 6459809920889663520000,6388752011759877221280000,10215614466804043676826720000,26417579011155256948273897920000

%N a(n) = (1/2)*Product_{k=0..n} (F(k)+2), where F=A000045 (Fibonacci numbers).

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

%t q[n_] := Fibonacci[n]

%t p[n_] := Product[q[k] + 2, {k, 0, n}]

%t Table[Simplify[p[n]/2], {n, 0, 20}]

%o (PARI) a(n) = prod(k=0, n, fibonacci(k)+2)/2; \\ _Michel Marcus_, Aug 04 2024

%Y Cf. A000045, A082480.

%K nonn

%O 0,2

%A _Clark Kimberling_, Aug 03 2024