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1, 4, 15151, 45154, 66466, 92629, 98689, 4976794, 6424246, 648616846, 136287949782631, 479573060375974, 69465717171756496, 4345218593958125434, 42097537753535773579024, 58071646151315164617085, 6220959179720279719590226
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Essentially the palindromes which are sums of three consecutive triangular numbers T.
Indices of the centered triangular numbers: 1, 2, 101, 174, 211, 249, 257, 1822, 2070, 20795, 9531980, 17880587, 215198695, ..., . [Robert G. Wilson v]
a(18) > 10^25. - Donovan Johnson, Sep 29 2011
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EXAMPLE
| T(99)+T(100)+T(101)=15151
T(172)+T(173)+T(174)= 45154
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MATHEMATICA
| n = 1; lst = {}; While[n < 10^10, ctn = 3 n (n - 1)/2 + 1; id = IntegerDigits@ ctn; If[id == Reverse@id, AppendTo[lst, ctn]; Print[{n, ctn}]]; n++ ]; lst [Robert G. Wilson v]
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CROSSREFS
| Cf. A005448, A000217.
Sequence in context: A134368 A152840 A003832 * A070157 A003556 A053015
Adjacent sequences: A162700 A162701 A162702 * A162704 A162705 A162706
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KEYWORD
| nonn,base
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AUTHOR
| Claudio L Meller (claudiomeller(AT)gmail.com), Jul 11 2009
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EXTENSIONS
| Edited and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl) and Robert G. Wilson v, (rgwv(AT)rgwv.com), Jul 13 2009
a(14)-a(17) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Sep 29 2011
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