OFFSET
1,3
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..10000
EXAMPLE
45 is in the sequence because (1) it is a triangular number and (2) the sum of its digits 4+5=9 is a square.
MATHEMATICA
Select[Accumulate[Range[0, 1000]], IntegerQ[Sqrt[Total[IntegerDigits[ #]]]]&] (* Harvey P. Dale, Dec 26 2014 *)
PROG
(PARI) isok(n) = ispolygonal(n, 3) && issquare(sumdigits(n)); \\ Michel Marcus, Feb 26 2014
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), Apr 26 2006
EXTENSIONS
Corrected by Michel Marcus, Feb 26 2014
STATUS
approved