%I M1784 #13 Nov 08 2017 08:51:09
%S 1,2,7,31,167,999,6495,44619,319463,2356406,17775821,136405506,
%T 1060866006,8339982193,66147792753,528559162227,4250413757583,
%U 34368723106860,279254390054538,2278795583070154,18667432144042678,153452484745198722
%N Number of P-graphs with 2n edges.
%D R. C. Read, On the enumeration of a class of plane multigraphs, Aequat. Math., 31 (1986), 47-63.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%F a(n) = (A003169(n) + 2 * A007165(n) + A007163(n)) / 4. - _Sean A. Irvine_, Nov 06 2017
%Y Cf. A003169, A007163, A007165.
%K nonn
%O 1,2
%A _N. J. A. Sloane_
%E a(5), a(9), a(10) corrected and more terms from _Sean A. Irvine_, Nov 06 2017