A005477 a(n) = 2^(n-1)*(2^n - 1)*Product_{j=1..n-1} (2^j + 1).

0, 1, 18, 420, 16200, 1138320, 152681760, 40012315200, 20727639504000, 21349793828563200, 43852643645542617600, 179883715700853141120000, 1474687052822610564537600000, 24170122236238340825650936320000

Offset

0,3

Links

G. C. Greubel, Table of n, a(n) for n = 0..75

Formula

a(n) = 2^(n-2)*(2^n - 1)*QPochhammer(n, -1, 2). - G. C. Greubel, Nov 25 2022

Maple

f := i->2^(i-1)*(2^i-1)*product( '2^j+1', 'j'=1..i-1);

Mathematica

Table[2^(n-1) (2^n-1)Product[2^j+1, {j, n-1}], {n, 0, 20}] (* Harvey P. Dale, Feb 02 2022 *)
Table[2^(n-2)*(2^n-1)*QPochhammer[-1, 2, n], {n, 0, 30}] (* G. C. Greubel, Nov 25 2022 *)

Prog

(Magma) [n le 1 select n else 2^(n-1)*(2^n -1)*(&*[2^j+1: j in [1..n-1]]): n in [0..25]]; // G. C. Greubel, Nov 25 2022
(SageMath)
def A005477(n): return 2^(n-2)*(2^n-1)*product(2^j+1 for j in range(n))
[A005477(n) for n in range(30)] # G. C. Greubel, Nov 25 2022

Crossrefs

Sequence in context: A318598 A215229 A172135 * A361549 A326368 A197343

Adjacent sequences: A005474 A005475 A005476 * A005478 A005479 A005480

Keyword

nonn

Author

N. J. A. Sloane

Extensions

a(0) prepended by G. C. Greubel, Nov 25 2022

Status

approved