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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

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

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Last modified November 22 18:55 EST 2019. Contains 329408 sequences. (Running on oeis4.)