A028694 25-factorial numbers.

1, 24, 14976, 233985024, 91400166014976, 892579654839833985024, 217914953902301689160166014976, 1330047325845938129350664710839833985024, 202949115880923695556030391039325175289160166014976, 774189437411767935420978172981557217629743778824710839833985024

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..37

Index entries for sequences related to factorial numbers.

Formula

From Amiram Eldar, Jul 14 2025: (Start)

a(n) = Product_{k=1..n} (25^k-1).

a(n) ~ c * 25^(n*(n+1)/2), where c = Product_{k>=1} (1 - 1/25^k) = 0.958400102563... . (End)

Mathematica

FoldList[ #1 (25^#2-1)&, 1, Range[ 20 ] ]
a[n_] := Abs[QPochhammer[25, 25, n]]; Array[a, 10, 0] (* Amiram Eldar, Jul 14 2025 *)

Prog

(PARI) a(n) = prod(k = 1, n, 25^k - 1); \\ Amiram Eldar, Jul 14 2025

Crossrefs

Cf. A005329, A027871, A027637, A027872, A027873, A027875, A027876, A027877, A027878, A027879, A027880, A028692, A028693.

Sequence in context: A377586 A159729 A341801 * A091777 A362712 A279299

Adjacent sequences: A028691 A028692 A028693 * A028695 A028696 A028697

Keyword

nonn

Author

Olivier Gérard

Status

approved