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A117309 Triangular numbers for which the sum of the digits is a hexagonal number. 1
0, 1, 6, 10, 15, 78, 105, 231, 276, 465, 528, 780, 861, 1176, 1275, 1653, 1770, 2211, 2346, 2850, 3003, 3570, 3741, 4371, 4560, 5253, 5460, 5995, 6216, 6441, 7260, 7503, 11175, 12246, 12561, 14028, 14878, 15225, 17205, 17578, 20301, 20706, 22155, 24090 (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

105 is in the sequence because (1) it is a triangular number and (2) the sum of its digits 1+0+5=6 is a hexagonal number.

MATHEMATICA

Join[{0}, Select[Accumulate[Range[350]], IntegerQ[(1+Sqrt[8Total[ IntegerDigits[#]]+1])/4]&]] (* Harvey P. Dale, Jun 06 2011 *)

CROSSREFS

Cf. A000217, A000384.

Sequence in context: A048078 A229276 A319035 * A228300 A299996 A315289

Adjacent sequences:  A117306 A117307 A117308 * A117310 A117311 A117312

KEYWORD

base,nonn

AUTHOR

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

EXTENSIONS

Corrected and extended by Harvey P. Dale, Jun 06 2011

STATUS

approved

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Last modified June 5 03:12 EDT 2020. Contains 334828 sequences. (Running on oeis4.)