A383227 a(n) is the product of first n even numbers not divisible by 5 (cf. A217562).

1, 2, 8, 48, 384, 4608, 64512, 1032192, 18579456, 408748032, 9809952768, 255058771968, 7141645615104, 228532659683328, 7770110429233152, 279723975452393472, 10629511067190951936, 446439464822019981312, 19643336452168879177728, 903593476799768442175488, 43372486886388885224423424

Offset: 0

Author

Stefano Spezia, Apr 20 2025

Keywords

• nonn

Crossrefs

Cf. A217562, A356858.

Programs

Mathematica

a[n_]:=Product[2*(i + Floor[(i-1)/4]),{i,n}]; Array[a,21,0]

Formula

a(n) = Product_{i=1..n} A217562(i).

a(n) = Product_{i=1..n} 2*(i + floor((i-1)/4)).