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 A243582 #14 Feb 16 2025 08:33:22 %S A243582 7,15,23,31,47,55,103 %N A243582 Integers of the form 8k+7 (A004771) that cannot be written as sum of four distinct squares. %H A243582 J. O. Sizemore, <a href="http://www.math.wisc.edu/~josizemore/Notes16%284-square%29.pdf">Lagrange's Four Square Theorem</a> %H A243582 R. C. Vaughan, <a href="https://personal.science.psu.edu/rcv4/Foursq.pdf">Lagrange's four-square theorem</a> %H A243582 Eric Weisstein's World of Math, <a href="https://mathworld.wolfram.com/LagrangesFour-SquareTheorem.html">Lagrange's Four-Square Theorem</a> %H A243582 Wikipedia, <a href="https://en.wikipedia.org/wiki/Lagrange%27s_four-square_theorem">Lagrange's four-square theorem</a> %e A243582 a(6) = 55 since 55 == 7 (mod 8) and all its representations as a sum of squares have duplicates, namely, 55=1^2+1^2+2^2+7^2, 55=1^2+2^2+5^2+5^2, 55=1^2+3^2+3^2+6^2. %Y A243582 Cf. A001948, A004771, A008586, A016813, A016825, A004767, A243577, A243578, A243579, A243580, A243581. %K A243582 nonn,fini,full %O A243582 1,1 %A A243582 _Walter Kehowski_, Jun 08 2014