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 A007162 Number of skeins with vertical symmetry. (Formerly M1766) 2
 1, 1, 2, 7, 24, 96, 388, 1667, 7278, 32726, 149232, 692014, 3244182, 15374906, 73474008, 353835147, 1714967402, 8360511370, 40964207460, 201630767026, 996494168808, 4943036743112, 24601517883704, 122815436413582, 614828204108840 (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 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 + H(x) * C(x) where H(x) = Sum_{k=1..infinity} A007165(k) * x^(2k) and C(x) = Sum_{k=0..infinity} A007161(k) * x^(2k+1). - Sean A. Irvine, Nov 06 2017 CROSSREFS Cf. A007161, A007165. Sequence in context: A150422 A137952 A005754 * A150423 A150424 A150425 Adjacent sequences: A007159 A007160 A007161 * A007163 A007164 A007165 KEYWORD nonn AUTHOR EXTENSIONS More terms from Sean A. Irvine, Nov 06 2017 STATUS approved

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Last modified January 29 02:42 EST 2023. Contains 359915 sequences. (Running on oeis4.)