A094873 n! has a triangular number of digits.

0, 1, 2, 3, 5, 6, 9, 13, 17, 32, 38, 44, 65, 106, 125, 135, 156, 178, 201, 213, 278, 292, 306, 335, 350, 381, 413, 446, 463, 480, 570, 589, 608, 647, 667, 687, 728, 749, 770, 880, 996, 1020, 1044, 1169, 1247, 1300, 1327, 1354, 1437, 1551, 1669, 1699, 1760

Offset: 0

Author

Jason Earls, Jun 16 2004

Keywords

• base
• nonn

Crossrefs

Cf. A000217, A006488.

Programs

Mathematica

Select[Range[0,1800],OddQ[Sqrt[1+8 IntegerLength[#!]]]&] (* Harvey P. Dale, Aug 07 2023 *)

Formula

{n: A034886(n) in A000217}. - R. J. Mathar, Nov 15 2019