This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A337759 #32 Sep 20 2020 01:27:44
%S A337759 49,81,121,169,196,225,289,324,361,441,484,529,625,676,729,784,841,
%T A337759 900,961,1089,1156,1225,1296,1369,1444,1521,1681,1764,1849,1936,2025,
%U A337759 2116,2209,2401,2500,2601,2704,2809,2916,3025,3136,3249,3364,3481,3600,3721,3844,3969
%N A337759 Squares that are the sum of 3 distinct nonzero squares.
%C A337759 These are the squares in A004432. - _Omar E. Pol_, Sep 18 2020
%F A337759 a(n) = A161992(n)^2. - _Andrew Howroyd_, Sep 18 2020
%e A337759 49 is a term because 6^2(36) + 3^2(9) + 2^2(4) = 7^2(49).
%e A337759 81 is a term because 8^2(64) + 4^2(16) + 1^2(1) = 9^2(81).
%e A337759 121 is a term because 9^2(81) + 6^2(36) + 2^2(4) = 11^2(121).
%e A337759 625 is a term because 9^2(81) + 12^2(144) + 20^2(400) = 25^2(625).
%t A337759 Select[Range[63]^2, Length @ Reduce[x^2 + y^2 + z^2 == # && 0 < x < y < z, {x, y, z}, Integers] > 0 &] (* _Amiram Eldar_, Sep 18 2020 *)
%Y A337759 Cf. A004432, A161992.
%K A337759 nonn
%O A337759 1,1
%A A337759 _Joseph Caliendo_, Sep 18 2020