A346386 Triangular numbers that are sum of squares of two distinct triangular numbers.

1, 10, 36, 45, 136, 325, 666, 820, 1225, 2080, 3321, 5050, 7381, 10440, 11026, 14365, 18721, 19306, 25425, 32896, 41905, 52650, 65341, 80200, 90100, 97461, 101025, 117370, 140185, 166176, 195625, 197506, 228826, 266085, 307720, 314821, 354061, 405450, 454581, 462241

Offset: 1

Author

Metin Sariyar, Jul 14 2021

Keywords

• nonn

Examples

			136, 10 and 6 are triangular numbers and 136 = 10^2 + 6^2 so 136 is a term.
820, 28 and 6 are triangular numbers and 820 = 28^2 + 6^2 so 820 is a term.
		

Crossrefs

Cf. A000217, A004431, A037270, A073613.

Programs

Mathematica

m = 50; t = Accumulate[Range[0, m]]; Select[Union[Plus @@@ Subsets[t^2, {2}]], # <= t[[-1]]^2 && IntegerQ @ Sqrt[8*# + 1] &] (* Amiram Eldar, Jul 16 2021 *)