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 A019438 #19 Jul 08 2025 07:31:21 %S A019438 1,2,3,5,6,7,11,14,15,23 %N A019438 Squarefree orders of elements of Mathieu group M_23. %C A019438 Numbers having a unique partition into four nonnegative squares. Let r=2, 6, or 14. Then the numbers r*4^k also have unique partitions into the four nonnegative squares for k>0. See A006431. - _T. D. Noe_, Aug 10 2005 %H A019438 D. H. Lehmer, <a href="http://www.jstor.org/stable/2305380">On the Partition of Numbers into Squares</a>, The American Mathematical Monthly, Vol. 55, No.8, October 1948, pp. 476-481. %H A019438 G. Nebe and M. Teider, <a href="https://dx.doi.org/10.1007/s00013-004-1288-4">Hecke actions on certain strongly modular genera of lattices</a>, Archiv der Mathematik 84 (1) (2005) 46-56. %H A019438 E. M. Rains and N. J. A. Sloane, <a href="http://neilsloane.com/doc/shad.html">The Shadow Theory of Modular and Unimodular Lattices</a>, J. Number Theory, 73 (1998), 359-389. %K A019438 nonn,fini,full %O A019438 0,2 %A A019438 _N. J. A. Sloane_