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A339298
Number of oriented series-parallel networks with n integer valued elements spanning an initial interval of positive integers and without multiple unit elements in parallel.
1
1, 3, 26, 339, 6241, 146261, 4192048, 141800728, 5532432894, 244530744314, 12076710992326, 659091388208810, 39390323152318533, 2558571976136883890, 179469998189344217166, 13520418589045722826274, 1088748555389998857776521, 93324804498600668393385498
OFFSET
1,2
COMMENTS
See A339297 for additional details.
PROG
(PARI) \\ See A339297 for R(n, k).
seq(n)={sum(k=1, n, R(n, k)*sum(r=k, n, binomial(r, k)*(-1)^(r-k)) )}
CROSSREFS
Row sums of A339297.
Cf. A339229.
Sequence in context: A357337 A227020 A119293 * A366315 A328269 A136046
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Dec 22 2020
STATUS
approved