

A007167


Number of skeins with 2n+1 edges.
(Formerly M3504)


0



1, 1, 4, 15, 62, 271, 1247, 5938, 29113, 145815, 743384, 3844314, 20118681, 106348391, 567002169, 3045455865, 16463622763, 89509216860, 489103356753, 2684663659765, 14795752770278, 81841297482116, 454202999050433, 2528381760697852
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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..23.
R. C. Read, On the enumeration of a class of plane multigraphs, Aequat. Math. 31 (1986) no 1, 4763.


PROG

(PARI) { s =y ; for(loop=1, 18, p = 1 ; forstep(i= 1, 2*loop1, 2, sigmai = polcoeff(s, i, y) ; if(i==2*loop1, print1(sigmai, ", ") ; ) ; n=0 ; tmp = 0 ; while(i*n <=2*loop1, ff = 1 ; for(k=1, n, ff *= (sigmaik+1)/k ; ) ; tmp += ff*(y)^(i*n) ; n++ ; ) ; p *= tmp : ) ; b = ys ; forstep(i=1, 2*loop1, 2, b += polcoeff(p, i, y)*y^i ; ) ; s = y ; for(r=0, loop1, for(i=0, 2*loop+1, s += polcoeff(b^(3+2*r), i, y)*y^i ; ) ; ) ; ) ; } \\ R. J. Mathar, Apr 24 2006


CROSSREFS

Sequence in context: A151484 A275871 A007161 * A036728 A027216 A124541
Adjacent sequences: A007164 A007165 A007166 * A007168 A007169 A007170


KEYWORD

nonn


AUTHOR

N. J. A. Sloane


EXTENSIONS

More terms from R. J. Mathar, Apr 24 2006
More terms from Sean A. Irvine, Nov 07 2017


STATUS

approved



