A002069 Palindromic pentagonal numbers. (Formerly M3924 N1612)

0, 1, 5, 22, 1001, 2882, 15251, 720027, 7081807, 7451547, 26811862, 54177145, 1050660501, 1085885801, 1528888251, 2911771192, 2376574756732, 5792526252975, 5875432345785, 10810300301801, 264571020175462, 5292834004382925, 10808388588380801, 15017579397571051

Offset

1,3

References

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Robert Price, Table of n, a(n) for n = 1..30

P. De Geest, More about Palindromic Pentagonals

A. Gloden and R. A. Johnson, Problem E427, Amer. Math. Monthly, 48 (1941), 211-212.

Mathematica

Select[PolygonalNumber[5, Range[0, 6*10^7]], PalindromeQ] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 15 2018 *)

Crossrefs

Cf. A028386, A000326.

Sequence in context: A299215 A300031 A271678 * A298233 A215742 A357948

Adjacent sequences: A002066 A002067 A002068 * A002070 A002071 A002072

Keyword

nonn,base

Author

N. J. A. Sloane

Status

approved