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

1,2

Links

Table of n, a(n) for n=1..31.

P. De Geest, Palindromic nonagonals

Formula

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

Mathematica

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

Crossrefs

Cf. A001106, A082723.

Sequence in context: A053457 A299112 A154030 * A237719 A369383 A108727

Adjacent sequences: A055557 A055558 A055559 * A055561 A055562 A055563

Keyword

nonn,base

Author

J. Lowell, Jul 10 2000

Extensions

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

Status

approved