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 A007161 Number of blobs with vertical symmetry. (Formerly M3503) 1
 1, 1, 4, 15, 62, 262, 1148, 5123, 23316, 107570, 502664, 2372786, 11302858, 54256236, 262226900, 1274944859, 6231845040, 30605344282, 150948390672, 747356368322, 3713140528364, 18506907541124, 92509837573736, 463660345091686 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Table of n, a(n) for n=0..23. 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^(2n+1) in x + D(x)^3/(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: A356942 A151484 A275871 * A352815 A007167 A036728 Adjacent sequences: A007158 A007159 A007160 * A007162 A007163 A007164 KEYWORD nonn AUTHOR N. J. A. Sloane. EXTENSIONS a(9) corrected and more terms from Sean A. Irvine, Nov 06 2017 STATUS approved

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Last modified May 21 08:24 EDT 2024. Contains 372729 sequences. (Running on oeis4.)