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 A180500 #7 Oct 07 2019 11:51:57 %S A180500 1,1,1,1,1,1,1,2,4,13,1,5,48,626,6570,1,25,1329,86715,4822394, %T A180500 181403533 %N A180500 Triangle read by row. T(n,m) gives the number of isomorphism classes of simple arrangements of n pseudolines and m double pseudolines in the projective plane. %D A180500 J. Ferté, V. Pilaud and M. Pocchiola, On the number of arrangements of five double pseudolines, Abstracts 18th Fall Workshop on Comput. Geom. (FWCG08), Troy, NY, October 2008. %H A180500 J. Ferté, V. Pilaud and M. Pocchiola, <a href="https://arxiv.org/abs/1009.1575">On the number of simple arrangements of five double pseudolines</a>, arXiv:1009.1575 [cs.CG], 2010; Discrete Comput. Geom. 45 (2011), 279-302. %Y A180500 See A180501 for isomorphism classes of all (not only simple) arrangements of n pseudolines and m double pseudolines in the projective plane. %Y A180500 See A180503 for isomorphism classes of simple arrangements of n pseudolines and m double pseudolines in the Moebius strip. %Y A180500 First diagonal gives A006248. %K A180500 nonn,tabl,more %O A180500 0,8 %A A180500 _Vincent Pilaud_, Sep 08 2010