A160473 The p(n) sequence that is associated with the Eta triangle A160464.

3, 30, 315, 11340, 311850, 12162150, 638512875, 86837751000, 7424627710500, 779585909602500, 98617617564716250, 14792642634707437500, 2596108782391155281250, 527010082825404522093750, 122529844256906551386796875, 64695757767646659132228750000

Offset: 2

Author

Johannes W. Meijer, May 24 2009

Keywords

• easy
• nonn

Crossrefs

A160464 is the Eta triangle.

Equals 3*(n-2)!*A000457(n-2)/A054243(n-1)

Equals 2^(-A049039(n-1))*(2*n-1)!

Cf. The pg(n) sequence A162440. - Johannes W. Meijer, Jul 06 2009

Programs

Magma

[2^(-(2*(n-1)-1-Floor(Log(n-1)/Log(2))))*Factorial(2*n-1)  : n in [2..30]]; // Vincenzo Librandi, Jul 06 2015

PARI

vector(20, n, n++; 2^(-(2*(n-1)-1-floor(log(n-1)/log(2))))*(2*n-1)!) \\ Michel Marcus, Jul 06 2015

Formula

a(n) = 2^(-(2*(n-1)-1-floor(log(n-1)/log(2))))*(2*n-1)! for n = 2, 3, 4, ... .