A291837 a(n) is the maximal value in row n of triangle A100960.
1, 6, 100, 3525, 210861, 20545920, 2516883516, 366723015750, 65231311386780, 13434052797314820, 3068032280097740670, 770387691039763211415, 222066633621598291951425, 69102739152239837029025040, 23037728813031184811224116360
Offset: 3
Keywords
Links
- Gheorghe Coserea, Table of n, a(n) for n = 3..126
- E. A. Bender, Z. Gao and N. C. Wormald, The number of labeled 2-connected planar graphs, Electron. J. Combin., 9 (2002), #R43.
Programs
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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); }; N=15; apply(p->vecmax(Vecrev(p)), Vec(A100960_ser(N+2)))
Comments