OFFSET
1,1
COMMENTS
A subsequence of A058957. Terms in the latter but not here are 45, 48, 63, 64, 72, 75, 80, 81, 96, 99, ... - M. F. Hasler, Apr 22 2015
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
EXAMPLE
9 is in the sequence because there are 2 solutions to x^2 - y^2 = 9, namely (x,y) = (3,0), (5,4).
MATHEMATICA
r[n_] := Reduce[x^2 - y^2 == n && x > y >= 0, {x, y}, Integers]; Reap[For[n = 1, n < 200, n++, rn = r[n]; If[rn[[0]] === Or && Length[rn] == 2, Print[n]; Sow[n]]]][[2, 1]] (* Jean-François Alcover, Apr 22 2015 *)
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Colin Barker, Apr 22 2015
STATUS
approved