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 A339230 Number of oriented series-parallel networks with integer valued elements summing to n. 2
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS See A339228 for additional details. LINKS EXAMPLE 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). PROG (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))} CROSSREFS Cf. A339228, A339229. Sequence in context: A091841 A063020 A104184 * A193621 A344623 A320180 Adjacent sequences: A339227 A339228 A339229 * A339231 A339232 A339233 KEYWORD nonn AUTHOR Andrew Howroyd, Nov 29 2020 STATUS approved

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Last modified March 22 02:41 EDT 2023. Contains 361413 sequences. (Running on oeis4.)