A216705 a(n) = Product_{k=1..n} (81 - 9/k).

1, 72, 5508, 429624, 33832890, 2679564888, 213025408596, 16981168285224, 1356370816782267, 108509665342581360, 8691624193940766936, 696910230823250585232, 55927046023565859464868, 4491372003738673637024784, 360913821729000560118063000

Offset

0,2

Comments

This sequence is generalizable: Product_{k=1..n} (q^2 - q/k) = (q^n/n!) * Product_{k=0..n-1} (q*k + q-1) = expansion of (1- x*q^2)^((1-q)/q).

Links

Harvey P. Dale, Table of n, a(n) for n = 0..524

Maple

seq(product(81-9/k, k=1.. n), n=0..20);
seq((9^n/n!)*product(9*k+8, k=0.. n-1), n=0..20);

Mathematica

Table[Product[81-9/k, {k, n}], {n, 0, 20}] (* Harvey P. Dale, Jul 20 2021 *)

Crossrefs

Cf. A004988, A049382, A004994, A216702, A216703, A216704.

Sequence in context: A103861 A358117 A358116 * A223148 A289368 A334357

Adjacent sequences: A216702 A216703 A216704 * A216706 A216707 A216708

Keyword

nonn

Author

Michel Lagneau, Sep 16 2012

Status

approved