A339230 Number of oriented series-parallel networks with integer valued elements summing to n.

1, 3, 9, 32, 120, 490, 2077, 9158, 41401, 191232, 897849, 4273794, 20573696, 99994830, 490000756, 2418246995, 12008813611, 59962351145, 300864703306, 1516196518032, 7670827035223, 38946578808655, 198379559337073, 1013452414823740, 5191372465942866, 26658747310696437

Offset: 1

Author

Andrew Howroyd, Nov 29 2020

Keywords

• nonn

Comments

See A339228 for additional details.

Examples

			In the following examples elements in series are juxtaposed and elements in parallel are separated by '|'.
a(1) = 1: (1).
a(2) = 3: (2), (11), (1|1).
a(3) = 9: (3), (12), (21), (1(1|1)), ((1|1)1), (111), (1|2), (1|11), (1|1|1).
		

Crossrefs

Cf. A339228, A339229.

Programs

PARI

EulerT(v)={Vec(exp(x*Ser(dirmul(v,vector(#v,n,1/n))))-1, -#v)}
EdgeWeightedT(u)={my(Z=x*Ser(u)); my(p=Z+O(x^2)); for(n=2, #u, p=x*Ser(EulerT(Vec(p^2/(1+p)+Z)))); Vec(p)}
seq(n)={EdgeWeightedT(vector(n,i,1))}