A139486 a(n) = Product_{j=0..n-1} (2^j + 2).

1, 3, 12, 72, 720, 12960, 440640, 29082240, 3780691200, 975418329600, 501365021414400, 514400511971174400, 1054521049540907520000, 4321427261018639016960000, 35409774976786728104970240000, 580224572769627326728042352640000

Offset: 0

Author

Leroy Quet, Apr 23 2008

Keywords

• easy
• nonn

Crossrefs

Cf. A139485, A028361.

Programs

PARI

{ a(n) = prod(j=0,n-1,2^j+2) }

Formula

a(n) = A139485(2^n + 1) - 1 = Sum_{j=1..2^n} A139485(j).

For n >= 1, a(n) = 2^(n-1) * 3 * A028361(n-1).

Extensions

Edited and extended by Max Alekseyev, Oct 24 2008