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A339230
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Number of oriented series-parallel networks with integer valued elements summing to n.
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2
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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
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OFFSET
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1,2
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COMMENTS
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See A339228 for additional details.
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LINKS
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Table of n, a(n) for n=1..26.
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EXAMPLE
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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).
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PROG
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(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))}
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CROSSREFS
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Cf. A339228, A339229.
Sequence in context: A091841 A063020 A104184 * A193621 A344623 A320180
Adjacent sequences: A339227 A339228 A339229 * A339231 A339232 A339233
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KEYWORD
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nonn
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AUTHOR
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Andrew Howroyd, Nov 29 2020
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STATUS
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approved
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