This site is supported by donations to The OEIS Foundation.



Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A007162 Number of skeins with vertical symmetry.
(Formerly M1766)

%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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

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