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A117305 Triangular numbers for which the sum of the digits is a pentagonal number. 0
0, 1, 10, 66, 435, 561, 741, 903, 1128, 1326, 1830, 2145, 2415, 3081, 5151, 6105, 7140, 10731, 11325, 12090, 12720, 13530, 15051, 19110, 20910, 30135, 31125, 33411, 50403, 53301, 70500, 81003, 100128, 130305, 142311, 180300, 200028, 220116 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..38.

EXAMPLE

66 is in the sequence because (1) it is a triangular number and (2) the sum of its digits 6+6=12 is a pentagonal number.

PROG

(PARI) isok(n) = ispolygonal(n, 3) && ispolygonal(sumdigits(n), 5); \\ Michel Marcus, Feb 26 2014

CROSSREFS

Cf. A000217, A000326.

Sequence in context: A163615 A232062 A229003 * A250790 A231886 A278090

Adjacent sequences:  A117302 A117303 A117304 * A117306 A117307 A117308

KEYWORD

base,nonn

AUTHOR

Luc Stevens (lms022(AT)yahoo.com), Apr 26 2006

STATUS

approved

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Last modified May 16 09:28 EDT 2021. Contains 343940 sequences. (Running on oeis4.)