0,3

Also number of 2-connected outerplanar graphs on n unlabeled nodes. - S. R. Finch (Steven.Finch(AT)inria.fr), Dec 09 2004

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

Guanzhang Hu, Group theory method for enumeration of outerplanar graphs, Acta Math. Appl. Sinica 14 (1998) 381-387.

P. Lisonek, Closed forms for the number of polygon dissections. Journal of Symbolic Computation 20 (1995), 595-601.

T. S. Motzkin, Relations between hypersurface cross ratios and a combinatorial formula for partitions of a polygon, for permanent preponderance and for non-associative products, Bull. Amer. Math. Soc., 54 (1948), 352-360.

R. C. Read, On general dissections of a polygon, Aequat. Math. 18 (1978), 370-388.

S. R. Finch, Planar graph growth constants.

f[x_, n_]:=x+Sum[(1/r)*Binomial[s-2, r-1]*Binomial[r+s-1, s]*x^s, {r, 1, n}, {s, 2, n}]; F[x_, n_]:=Series[((3x^2-2*x*f[x, n]+f[x, n]^2)- (2+2*x+7*x^2-4*x*f[x, n]+2*f[x, n]^2)*f[x^2, n]+ 2*f[x^2, n]^2)/(4*(2*f[x^2, n]-1))+Sum[If[Mod[k, d]==0, EulerPhi[d]*f[x^d, n]^(k/d)/k, 0], {k, 3, n}, {d, 1, k}]/2, {x, 0, n}]; F[x, 22] (Finch)

Adjacent sequences: A001001 A001002 A001003 this_sequence A001005 A001006 A001007

Sequence in context: A097075 A036673 A111189 this_sequence A015951 A101531 A099607

nonn,nice,easy

N. J. A. Sloane (njas(AT)research.att.com).

More terms from Esa Peuha (esa.peuha(AT)helsinki.fi), Oct 21 2005