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 A229140 #30 Jul 08 2025 11:28:03 %S A229140 0,0,1,0,1,2,0,1,2,0,1,3,2,0,1,2,4,3,0,1,2,4,3,0,1,4,2,3,5,0,1,2,6,3, %T A229140 5,4,0,1,2,5,3,4,7,0,1,2,5,3,7,4,6,0,1,2,8,3,6,4,0,1,5,2,7,3,6,4,9,8, %U A229140 0,1,2,3,6,9,4,7,5,0,1,2,9,3,8,4,7,5,0 %N A229140 Smallest k such that k^2 + l^2 = n-th number expressible as sum of two squares (A001481). %C A229140 Conjecture: the values between two zeros are always distinct from each other. %F A229140 a(n) = 0 if A001481(n) is square. %F A229140 a(n) = sqrt(A001481(n)-A385236(n)^2). - _Zhuorui He_, Jul 08 2025 %e A229140 The 6th number expressible as sum of two squares A001481(6) = 8 = 2^2 + 2^2, so a(6)=2. %o A229140 (PARI) for(n=0, 300, s=sqrtint(n); forstep(i=s, 0, -1, if(issquare(n-i*i), print1(sqrtint(n-i*i), ", "); break))); \\ shift corrected by _Michel Marcus_, Jul 08 2025 %Y A229140 Cf. A001481, A385236 (largest k), A385237, A283303, A283304. %K A229140 nonn %O A229140 1,6 %A A229140 _Ralf Stephan_, Sep 15 2013