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 A273123 #18 May 22 2016 00:13:53 %S A273123 85,130,340,520,1360,2080,5440,8320,21760,33280,87040,133120,348160, %T A273123 532480,1392640,2129920,5570560,8519680,22282240,34078720,89128960, %U A273123 136314880,356515840,545259520,1426063360,2181038080,5704253440,8724152320 %N A273123 Values of A007692(n) that are not of the form x^2 + y^2 + z^2 where x, y, z are nonzero integers. %C A273123 If n is in this sequence, then 4*n is also in this sequence. So 85*4^k and 130*4^k are terms of this sequence for all nonnegative values of k. %C A273123 For more details see A051952. %e A273123 85 is a term because 85 = 2^2 + 9^2 = 6^2 + 7^2 and 85 = x^2 + y^2 + z^2 has no solution for nonzero integer values of x, y, z. %e A273123 130 is a term because 130 = 3^2 + 11^2 = 7^2 + 9^2 and 130 = x^2 + y^2 + z^2 has no solution for nonzero integer values of x, y, z. %e A273123 340 is a term because 340 = 4*85 and 85 is a term. %t A273123 twoQ[n_] := 2 == Length@ Select[ PowersRepresentations[n, 2, 2], Times @@ # > 0 &, 2]; threeQ[n_] := {} != Quiet@ IntegerPartitions[n, {3}, Range[ Sqrt@ n]^2, 1]; Select[Range[10^5], twoQ[#] && ! threeQ[#] &] (* _Giovanni Resta_, May 16 2016 *) %Y A273123 Cf. A000408, A004214, A007692, A051952. %K A273123 nonn %O A273123 1,1 %A A273123 _Altug Alkan_, May 16 2016 %E A273123 a(14)-a(28) from _Giovanni Resta_, May 16 2016