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 A007163 Number of P-graphs with vertical symmetry. (Formerly M2854) 1
 1, 3, 10, 39, 158, 674, 2944, 13191, 60078, 277890, 1300536, 6151078, 29346036, 141088632, 682825140, 3324172359, 16267134462, 79975707362, 394833880540, 1956620531762, 9729300574580, 48529814786620, 242757311049680, 1217508537475894 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS R. C. Read, On the enumeration of a class of plane multigraphs, Aequat. Math. 31 (1986) no 1, 47-63. FORMULA a(n) = coefficient of x^(2*n) in D(x)^2 / (1-D(x)^2) where D(x) = Sum_{k=0..infinity} A007162(k) * x^(2*k+1). - Sean A. Irvine, Nov 06 2017 CROSSREFS Cf. A007162. Sequence in context: A151065 A151066 A151067 * A219263 A050385 A296195 Adjacent sequences:  A007160 A007161 A007162 * A007164 A007165 A007166 KEYWORD nonn AUTHOR EXTENSIONS a(9)-a(10) corrected and more terms from Sean A. Irvine, Nov 06 2017 STATUS approved

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Last modified December 16 00:33 EST 2019. Contains 330013 sequences. (Running on oeis4.)