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 A320491 #10 Jan 28 2020 15:01:26 %S A320491 1,2,0,4,13,98,748,9982,205290,6546960,352371887,29668304472, %T A320491 4303531187466,985391751078694,391866509275972993, %U A320491 248491878411568471280,274544424465100159954078,488310442484985365942048784,1513516279388226593561422201905 %N A320491 Number of connected edge-self-dual nets with n nodes. %H A320491 Edward A. Bender and E. Rodney Canfield, <a href="https://doi.org/10.1016/0095-8956(83)90040-0">Enumeration of connected invariant graphs</a>, Journal of Combinatorial Theory, Series B 34.3 (1983): 268-278. See p. 275. %H A320491 Andrew Howroyd, <a href="/A320491/a320491.txt">PARI Program</a> %F A320491 a(2*n-1) = b(2*n-1), a(2*n) = b(2*n) - (A320489(n) - a(n))/2 where b is the Inverse Euler transform of A004106. %o A320491 (PARI) \\ See link for program. %o A320491 A320491seq(20) \\ _Andrew Howroyd_, Jan 28 2020 %Y A320491 Cf. A004103 (nets), A004106 (edge-self-dual), A320489 (connected nets). %K A320491 nonn %O A320491 0,2 %A A320491 _N. J. A. Sloane_, Oct 25 2018 %E A320491 Dead sequence restored, corrected and extended by _Andrew Howroyd_, Jan 28 2020