A055560 Base numbers of 9-gonal palindromic numbers.

1, 2, 6, 12, 17, 44, 74, 139, 1123, 1411, 2101, 4070, 11323, 11472, 12870, 16318, 16853, 18729, 52642, 132619, 435644, 446904, 168566853, 350096787, 521037077, 708609429, 1121857192, 1641773578, 11947307367, 21633254881, 75356090494

Offset: 1

Author

J. Lowell, Jul 10 2000

Keywords

• nonn
• base

Links

• P. De Geest, Palindromic nonagonals

Crossrefs

Cf. A001106, A082723.

Programs

Mathematica

Select[Range[0, 10^5], PalindromeQ[PolygonalNumber[9, #]] &] (* Robert Price, Apr 29 2019 *)

Formula

9-gonal numbers are of the form (n(7n-5))/2.

Extensions

Edited and extended by Patrick De Geest, Apr 13 2003.