OFFSET
1,3
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
26569 = 163^2 is in the sequence because it is a square and the sum of its digits, 2+6+5+6+9 = 28, is a triangular number.
MATHEMATICA
Select[Range[0, 361]^2, IntegerQ @ Sqrt[8 * Plus @@ IntegerDigits[#] + 1] &] (* Amiram Eldar, Mar 24 2021 *)
PROG
(PARI) isok(n) = issquare(n) && ispolygonal(sumdigits(n), 3); \\ Michel Marcus, Feb 27 2014
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), May 05 2006
STATUS
approved