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 A221961 #11 Feb 24 2018 10:12:16 %S A221961 1,3,18,149,1390,13377 %N A221961 Number of n X n symmetric lonesum ternary matrices. %H A221961 H. K. Kim, D. S. Krotov and J. Y. Lee, <a href="http://dx.doi.org/10.1016/j.laa.2012.11.027">Matrices uniquely determined by their lonesums</a>, Linear Algebra and its Applications, 438 (2013) no 7, 3107-3123 %F A221961 Kim et al. (2013) give a formula. %Y A221961 Cf. A000629 (the binary case). %Y A221961 See also A299906, A299907 for the general binary case. %K A221961 nonn,more %O A221961 0,2 %A A221961 _N. J. A. Sloane_, Feb 05 2013