A007161 Number of blobs with vertical symmetry. (Formerly M3503)

1, 1, 4, 15, 62, 262, 1148, 5123, 23316, 107570, 502664, 2372786, 11302858, 54256236, 262226900, 1274944859, 6231845040, 30605344282, 150948390672, 747356368322, 3713140528364, 18506907541124, 92509837573736, 463660345091686

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.

Formula

a(n) = coefficient of x^(2n+1) in x + D(x)^3/(1-D(x)^2) where D(x) = Sum_{k=0..infinity} A007162(k) * x^(2*k+1). - Sean A. Irvine, Nov 06 2017

Crossrefs

Cf. A007162.

Sequence in context: A356942 A151484 A275871 * A352815 A007167 A036728

Adjacent sequences: A007158 A007159 A007160 * A007162 A007163 A007164

Keyword

nonn

Author

N. J. A. Sloane.

Extensions

a(9) corrected and more terms from Sean A. Irvine, Nov 06 2017

Status

approved