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

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

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..24.

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

N. J. A. Sloane.

Extensions

More terms from Sean A. Irvine, Nov 06 2017

Status

approved