OFFSET
2,1
LINKS
Gheorghe Coserea, Table of n, a(n) for n = 2..55001
E. A. Bender, Z. Gao and N. C. Wormald, The number of labeled 2-connected planar graphs, Electron. J. Combin., 9 (2002), #R43.
FORMULA
EXAMPLE
26.18411255565814849687701423391145...
PROG
(PARI)
x(t) = (1+3*t)*(1/t-1)^3/16;
y(t) = {
my(y1 = t^2 * (1-t) * (18 + 36*t + 5*t^2),
y2 = 2 * (3+t) * (1+2*t) * (1+3*t)^2);
(1+2*t)/((1+3*t) * (1-t)) * exp(-y1/y2) - 1;
};
N=80; default(realprecision, N+100); t0=solve(t=.62, .63, y(t)-1);
r=1/x(t0); eval(select(x->(x != "."), Vec(Str(r))[1..-101]))
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Gheorghe Coserea, Sep 03 2017
STATUS
approved