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
KEYWORD
base,nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), Apr 26 2006
STATUS
approved