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A055560 Base numbers of 9-gonal palindromic numbers. 4
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 (list; graph; refs; listen; history; text; internal format)
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 A108727 A138630

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

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Last modified January 26 23:54 EST 2022. Contains 350601 sequences. (Running on oeis4.)