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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
OFFSET
0,3
LINKS
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
Sequence in context: A048078 A229276 A319035 * A228300 A342480 A299996
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