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A007162 Number of skeins with vertical symmetry.
(Formerly M1766)
2

%I M1766

%S 1,1,2,7,24,96,388,1667,7278,32726,149232,692014,3244182,15374906,

%T 73474008,353835147,1714967402,8360511370,40964207460,201630767026,

%U 996494168808,4943036743112,24601517883704,122815436413582,614828204108840

%N Number of skeins with vertical symmetry.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H R. C. Read, <a href="http://dx.doi.org/10.1007/BF02188172">On the enumeration of a class of plane multigraphs</a>, Aequat. Math. 31 (1986) no 1, 47-63.

%F 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

%Y Cf. A007161, A007165.

%K nonn

%O 0,3

%A _N. J. A. Sloane_.

%E More terms from _Sean A. Irvine_, Nov 06 2017

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Last modified December 5 17:42 EST 2019. Contains 329768 sequences. (Running on oeis4.)