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 A334457 #17 May 06 2020 01:33:42 %S A334457 4,5,6,9,11,13,16 %N A334457 Block sizes k of nontrivial biplanes. %C A334457 A biplane is an incidence structure consisting of a set P of h points and a set of h blocks, each of which is an k-subset of P (block size k), such that every pair of points lies in exactly 2 blocks (see Alavi et al.). %H A334457 Seyed Hassan Alavi, Ashraf Daneshkhah, Cheryl E Praeger, <a href="https://arxiv.org/abs/2004.04535">Symmetries of biplanes</a>, arXiv:2004.04535 [math.GR], 2020. See Introduction p. 1. %H A334457 P. Kaski and P. R. J. Östergård. <a href="https://doi.org/10.1002/jcd.20145">There are exactly five biplanes with k = 11</a>, J. Combin. Des., 16(2):117-127, 2008. %Y A334457 Cf. A001109, A003409, A038723, A038725, A054490, A334456 (h). %K A334457 nonn,more %O A334457 1,1 %A A334457 _Stefano Spezia_, Apr 30 2020