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A117312 Triangular numbers for which the sum of the digits is a heptagonal number. 1
0, 1, 10, 378, 666, 990, 1485, 1953, 2556, 2628, 4095, 4851, 4950, 6903, 9045, 9180, 10296, 11628, 11781, 14535, 14706, 16290, 19503, 19701, 21528, 23436, 25425, 27261, 29403, 31626, 33930, 34191, 36315, 39060, 41328, 41616, 44253, 52326 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Harvey P. Dale, Table of n, a(n) for n = 0..1000

EXAMPLE

378 is in the sequence because (1) it is a triangular number and (2) the sum of its digits 3+7+8=18 is a heptagonal number.

MATHEMATICA

Join[{0}, Select[Accumulate[Range[0, 500]], IntegerQ[(3+Sqrt[40*Total[ IntegerDigits[ #]]+9])/10]&]] (* Harvey P. Dale, Aug 10 2013 *)

CROSSREFS

Cf. A000217, A000566.

Sequence in context: A117797 A301311 A291530 * A200804 A277663 A000591

Adjacent sequences:  A117309 A117310 A117311 * A117313 A117314 A117315

KEYWORD

base,nonn

AUTHOR

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

STATUS

approved

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Last modified August 4 15:50 EDT 2020. Contains 336202 sequences. (Running on oeis4.)