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A115682
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Triangular numbers whose digit reversal is a pentagonal number (A000326).
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0
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1, 10, 15, 21, 210, 62481, 67896, 557040, 2618616, 10095771, 10550121, 28883800, 62490610, 1524872700, 2708516800, 5491258003, 103352174628, 299536839001, 24709216250400, 7220385308804403, 7686108558349885, 10917127849295955, 15038347789610970, 23424201805125660
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OFFSET
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1,2
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LINKS
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EXAMPLE
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62481=T(353) and 18426 is the 111th pentagonal number.
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PROG
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(PARI) lista(nn) = {for(n=1, nn, t = n*(n+1)/2; if (ispolygonal(subst(Polrev(digits(t)), x, 10), 5), print1(n*(n+1)/2, ", ")); ); } \\ Michel Marcus, Apr 16 2014
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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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