A007166 Number of blobs with 2n+1 edges. (Formerly M1777)

1, 1, 2, 7, 27, 118, 537, 2570, 12587, 63173, 322385, 1669144, 8742999, 46253727, 246771340, 1326236480, 7173280391, 39017312543, 213287030596, 1171140510636, 6456473371424, 35723687996130, 198311302682834, 1104189489401230

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, 47-63.

Prog

(PARI) { s =y ; for(loop=1, 18, p = 1 ; forstep(i= 1, 2*loop-1, 2, sigmai = polcoeff(s, i, y) ; n=0 ; tmp = 0 ; while(i*n <=2*loop-1, ff = 1 ; for(k=1, n, ff *= (-sigmai-k+1)/k ; ) ; tmp += ff*(-y)^(i*n) ; n++ ; ) ; p *= tmp : ) ; b = y-s ; forstep(i=1, 2*loop-1, 2, b += polcoeff(p, i, y)*y^i ; ) ; print1(polcoeff(b, 2*loop-1, y), ", ") ; s = y ; for(r=0, loop-1, 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: A150642 A150643 A150644 * A036783 A368762 A150645

Adjacent sequences: A007163 A007164 A007165 * A007167 A007168 A007169

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