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 A381961 #30 Mar 22 2025 15:46:03 %S A381961 1,1,1,2,6,6,14,25,60,124,302,696,1745,4300,11042,28362,74483,196539, %T A381961 525521,1413635,3835932,10468384 %N A381961 Number of connected graphs with n vertices which have a planar square. %C A381961 See A382180 for a definition of a square graph. %C A381961 For a graph to have a planar square, it must also be planar itself. Further, the degree of every vertex must be <= 3 and the graph must have no 5-cycles. %H A381961 Frank Harary, Richard M. Karp, and William T. Tutte, <a href="https://doi.org/10.1016/S0021-9800(67)80050-4">A Criterion for Planarity of the Square of a Graph</a>, J. Comb. Th., 2, 1967, pp. 395-405. %Y A381961 Cf. A382180, A382181, A382284. %K A381961 nonn,hard,more %O A381961 0,4 %A A381961 _Sean A. Irvine_, Mar 18 2025 %E A381961 a(16)-a(20) from _Brendan McKay_, Mar 21 2025 %E A381961 a(21) from _Sean A. Irvine_, Mar 22 2025