A007162 Number of skeins with vertical symmetry.

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

Author

N. J. A. Sloane

Keywords

• nonn

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.

Crossrefs

Cf. A007161, A007165.

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

Extensions

More terms from Sean A. Irvine, Nov 06 2017