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1, 4, 15151, 45154, 66466, 92629, 98689, 4976794, 6424246, 648616846, 136287949782631, 479573060375974, 69465717171756496, 4345218593958125434, 42097537753535773579024, 58071646151315164617085, 6220959179720279719590226, 458122911526080625119221854
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OFFSET
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1,2
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COMMENTS
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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, ..., (A195903). - Robert G. Wilson v
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LINKS
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FORMULA
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a(n) = (3*m^2 - 3*m + 2)/2 or a(n) = (3*n^2 + 3*n + 2)/2 with n = m - 1.
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EXAMPLE
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T(99) + T(100) + T(101) = 15151.
T(172) + T(173) + T(174) = 45154.
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MATHEMATICA
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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
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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