OFFSET
1,1
COMMENTS
It is assumed here that 0 is a square but not a triangular number. - Amiram Eldar, Dec 08 2019
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
a(4) = 26 because 26 = 1 + 25; 26 = 10 + 16.
MATHEMATICA
aQ[n_] := Length @ Solve[x^2 + y (y + 1)/2 == n && x >= 0 && y > 0, {x, y}, Integers] == 2; Select[Range[250], aQ] (* Amiram Eldar, Dec 08 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Earls, May 17 2003
EXTENSIONS
Name clarified by Amiram Eldar, Dec 08 2019
STATUS
approved