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A002069 Palindromic pentagonal numbers.
(Formerly M3924 N1612)
2
0, 1, 5, 22, 1001, 2882, 15251, 720027, 7081807, 7451547, 26811862, 54177145, 1050660501, 1085885801, 1528888251, 2911771192, 2376574756732, 5792526252975, 5875432345785, 10810300301801, 264571020175462, 5292834004382925 (list; graph; refs; listen; history; text; internal format)
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

Table of n, a(n) for n=1..22.

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 A120488

Adjacent sequences:  A002066 A002067 A002068 * A002070 A002071 A002072

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified November 17 20:57 EST 2018. Contains 317278 sequences. (Running on oeis4.)