A277355 a(n) = Product_{k=1..n} (2^k + k).

1, 3, 18, 198, 3960, 146520, 10256400, 1384614000, 365538096000, 190445348016000, 196920489848544000, 405459288598152096000, 1665626757561208810368000, 13666467545789718289069440000, 224102734815859800504160677120000, 7346759955468331839927899478024960000

Offset: 0

Author

Vaclav Kotesovec, Oct 10 2016

Keywords

• nonn

Crossrefs

Cf. A005329, A028362.

Programs

Mathematica

Table[Product[2^k+k, {k, 1, n}], {n, 0, 15}]

Formula

a(n) ~ c * 2^(n*(n+1)/2), where c = Product_{k>=1} (1 + k/2^k) = 5.52995584900...