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 A007164 Number of P-graphs with 2n edges. (Formerly M1784) 0
 1, 2, 7, 31, 167, 999, 6495, 44619, 319463, 2356406, 17775821, 136405506, 1060866006, 8339982193, 66147792753, 528559162227, 4250413757583, 34368723106860, 279254390054538, 2278795583070154, 18667432144042678, 153452484745198722 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES R. C. Read, On the enumeration of a class of plane multigraphs, Aequat. Math., 31 (1986), 47-63. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS FORMULA a(n) = (A003169(n) + 2 * A007165(n) + A007163(n)) / 4. - Sean A. Irvine, Nov 06 2017 CROSSREFS Cf. A003169, A007163, A007165. Sequence in context: A105216 A260532 A193657 * A321208 A005977 A199675 Adjacent sequences:  A007161 A007162 A007163 * A007165 A007166 A007167 KEYWORD nonn AUTHOR EXTENSIONS a(5), a(9), a(10) corrected and more terms from Sean A. Irvine, Nov 06 2017 STATUS approved

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Last modified December 8 14:38 EST 2019. Contains 329865 sequences. (Running on oeis4.)