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A003098 Palindromic triangular numbers.
(Formerly M2605)
14
1, 3, 6, 55, 66, 171, 595, 666, 3003, 5995, 8778, 15051, 66066, 617716, 828828, 1269621, 1680861, 3544453, 5073705, 5676765, 6295926, 35133153, 61477416, 178727871, 1264114621, 1634004361, 5289009825, 6172882716, 13953435931 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

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

Charles W. Trigg, Palindromic Triangular Numbers, J. Rec. Math., 6 (1973), 146-147.

David Wells, The Penguin Dictionary of Curious and Interesting Numbers, p. 73 (Rev. ed. 1997)

LINKS

T. D. Noe, Table of n, a(n) for n=1..147 (from P. De Geest)

P. De Geest, Palindromic Triangulars

MATHEMATICA

palQ[n_]:=Module[{idn=IntegerDigits[n]}, idn==Reverse[idn]]; Select[Accumulate[Range[200000]], palQ]  (* Harvey P. Dale, Mar 23 2011 *)

CROSSREFS

Cf. A008509, A002113, A000217.

Sequence in context: A032070 A066569 A051641 * A045914 A067610 A067609

Adjacent sequences:  A003095 A003096 A003097 * A003099 A003100 A003101

KEYWORD

nonn,base,easy,nice

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified July 30 23:15 EDT 2014. Contains 245076 sequences.