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%I #11 Dec 08 2019 12:25:11
%S 7,15,22,26,28,31,40,45,52,55,59,61,67,79,85,87,92,94,100,102,103,106,
%T 114,115,124,130,140,142,147,155,157,159,166,175,178,180,184,187,189,
%U 190,191,197,202,205,206,210,211,214,220,224,231,232,240,241,246,247
%N Integers expressible as the sum of a square and a triangular number in exactly two distinct ways.
%C It is assumed here that 0 is a square but not a triangular number. - _Amiram Eldar_, Dec 08 2019
%H Amiram Eldar, <a href="/A082658/b082658.txt">Table of n, a(n) for n = 1..10000</a>
%e a(4) = 26 because 26 = 1 + 25; 26 = 10 + 16.
%t 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 *)
%Y Cf. A000217, A000290, A082657, A082659, A082660.
%K nonn
%O 1,1
%A _Jason Earls_, May 17 2003
%E Name clarified by _Amiram Eldar_, Dec 08 2019
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