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A346386
Triangular numbers that are sum of squares of two distinct triangular numbers.
0
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
1,2
EXAMPLE
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.
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 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Metin Sariyar, Jul 14 2021
STATUS
approved