OFFSET
1,3
COMMENTS
Row n >= 3 contains 3*n-5 terms.
LINKS
Gheorghe Coserea, Rows n = 1..126, flattened
E. A. Bender, Z. Gao and N. C. Wormald, The number of labeled 2-connected planar graphs, Electron. J. Combin., 9 (2002), #R43.
M. Bodirsky, C. Groepl and M. Kang, Generating Labeled Planar Graphs Uniformly At Random, Theoretical Computer Science, Volume 379, Issue 3, 15 June 2007, Pages 377-386.
Omer Gimenez, Marc Noy, Asymptotic enumeration and limit laws of planar graphs, J. Amer. Math. Soc. 22 (2009), 309-329.
FORMULA
EXAMPLE
A(x;t) = x + t*x^2/2! + (3*t^2 + t^3)*x^3/3! + (16*t^3 + 15*t^4 + 6*t^5 + t^6)*x^4/4! + ...
Triangle starts:
n\k [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
[1] 1;
[2] 0 1;
[3] 0, 0, 3, 1;
[4] 0, 0, 0, 16, 15, 6, 1;
[5] 0, 0, 0, 0, 125, 222, 205, 120, 45, 10;
[6] 0, 0, 0, 0, 0, 1296, 3660, 5700, 6165, 4935, 2937, 1125, 195;
[7] ...
PROG
(PARI)
Q(n, k) = { \\ c-nets with n-edges, k-vertices
if (k < 2+(n+2)\3 || k > 2*n\3, return(0));
sum(i=2, k, sum(j=k, n, (-1)^((i+j+1-k)%2)*binomial(i+j-k, i)*i*(i-1)/2*
(binomial(2*n-2*k+2, k-i)*binomial(2*k-2, n-j) -
4*binomial(2*n-2*k+1, k-i-1)*binomial(2*k-3, n-j-1))));
};
A100960_ser(N) = {
my(x='x+O('x^(3*N+1)), t='t+O('t^(N+4)),
q=t*x*Ser(vector(3*N+1, n, Polrev(vector(min(N+3, 2*n\3), k, Q(n, k)), 't))),
d=serreverse((1+x)/exp(q/(2*t^2*x) + t*x^2/(1+t*x))-1),
g2=intformal(t^2/2*((1+d)/(1+x)-1)));
serlaplace(Ser(vector(N, n, subst(polcoeff(g2, n, 't), 'x, 't)))*'x);
};
A288265_ser(N) = {
my(x='x+O('x^(N+3)), b = t*x^2/2 + serconvol(A100960_ser(N), exp(x)),
g1=intformal(serreverse(x/exp(b'))/x)); serlaplace(g1);
};
A288265_seq(N) = {
my(v=Vec(A288265_ser(N))); vector(#v, n, Vecrev(v[n]/t^(n-1)));
};
concat(A288265_seq(9))
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Gheorghe Coserea, Aug 14 2017
STATUS
approved