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 A187928 #37 Nov 25 2024 20:44:39 %S A187928 1,2,4,15,42,135,440,1480,5106,17890,63264,226018,812354,2936837, %T A187928 10666188,38901190,142386358 %N A187928 Number of embeddings on the sphere of planar graphs with n edges having connectivity exactly 2 and minimum vertex degree at least 3. %C A187928 The graphs are 2-connected, but not 3-connected. The graphs were enumerated using plantri (by B.D. McKay & G. Brinkmann) for the purpose of finding compound perfect squared squares. If all graphs with n edges are generated then all compound squares in order n-1 can be obtained from them. Graphs with minimum degree at least 3 are also called homeomorphically irreducible. %H A187928 Stuart Anderson, <a href="http://www.squaring.net/sq/ss/cpss/cpss.html">Compound Perfect Squared Squares</a> %H A187928 B. D. McKay and G. Brinkmann, <a href="http://users.cecs.anu.edu.au/~bdm/plantri/plantri-guide.txt">Plantri Guide</a> %H A187928 Gunnar Brinkmann and Brendan McKay, <a href="/A007021/a007021.txt">Guide to using plantri</a> [Cached copy, with permission] %o A187928 (plantri) %o A187928 plantri -p -c2 -m3 -e# -x -u -v n %o A187928 (plantri) %o A187928 plantri -pc2m3e#xuv n # to count graphs by node number (n) and edge number (#) %Y A187928 Antidiagonal sums of A378077. %Y A187928 Cf. A034889, A181340, A187927, A021103, A378076. %K A187928 nonn,more,hard %O A187928 10,2 %A A187928 _Stuart E Anderson_, Mar 16 2011 %E A187928 a(22) corrected by _Stuart E Anderson_, Feb 24 2013 %E A187928 a(23)-a(26) from _Lorenz Milla_, Oct 08 2013 %E A187928 a(11) corrected by _Andrew Howroyd_, Nov 15 2024