A028680 Pseudo Galois numbers for d=18.

1, 306, 32023512, 1089004102288704, 12000667955029147591142400, 42847968954950283704312619696092774400, 49567873660106321460531697392097352394556112948428800, 18578701620081137383821309406407591330835087924034550043168000809369600

Offset: 0

Author

Olivier Gérard

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..28

Crossrefs

Cf. A028668, A028670, A028671, A028672, A028674, A028676, A028677, A028678, A028682, A028683, A028684, A028686.

Programs

Mathematica

FoldList[ #1*18^#2 (18^#2-1)&, 1, Range[ 20 ] ]
a[n_] := 18^n * Product[18^n - 18^k, {k, 0, n-1}]; Array[a, 8, 0] (* Amiram Eldar, Jul 14 2025 *)

PARI

a(n) = 18^n * prod(k = 0, n-1, 18^n - 18^k); \\ Amiram Eldar, Jul 14 2025

Formula

a(n) = 18^n * Product_{k=0..n-1} (18^n - 18^k).

a(n) ~ c * 18^(n^2+n), where c = Product_{k>=1} (1 - 1/18^k) = 0.941358555546... . - Amiram Eldar, Jul 14 2025