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A115682 Triangular numbers whose digit reversal is a pentagonal number (A000326). 0
1, 10, 15, 21, 210, 62481, 67896, 557040, 2618616, 10095771, 10550121, 28883800, 62490610, 1524872700, 2708516800, 5491258003, 103352174628, 299536839001, 24709216250400, 7220385308804403, 7686108558349885, 10917127849295955, 15038347789610970, 23424201805125660 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..24.

EXAMPLE

62481=T(353) and 18426 is the 111th pentagonal number.

PROG

(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

CROSSREFS

Cf. A000326.

Sequence in context: A048028 A048045 A257631 * A075523 A115679 A109373

Adjacent sequences:  A115679 A115680 A115681 * A115683 A115684 A115685

KEYWORD

nonn,base

AUTHOR

Giovanni Resta, Jan 31 2006

EXTENSIONS

a(19)-a(24) from Michel Marcus, Apr 16 2014

STATUS

approved

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Last modified August 21 18:26 EDT 2019. Contains 326168 sequences. (Running on oeis4.)