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A339300 Number of essentially parallel oriented series-parallel networks with n labeled elements and without multiple unit elements in parallel. 2
1, 0, 6, 36, 540, 8400, 169680, 3966480, 107518320, 3295283040, 112888369440, 4272403544640, 177061349424960, 7974538914101760, 387840385867334400, 20257533315635616000, 1130954856127948051200, 67208532822729871372800, 4235759061057115720128000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

See A339301 for additional details.

LINKS

Table of n, a(n) for n=1..19.

FORMULA

E.g.f. (1 + x)*exp(S(x)) - S(x) - 1 where S(x) is the e.g.f. of A339299.

E.g.f.: B(x)/(1 + B(x)) where B(x) is the e.g.f. of A339301.

E.g.f.: B(log(1+x)) where B(x) is the e.g.f. of A048174.

PROG

(PARI) seq(n, Z=x)={my(p=Z+O(x^2)); for(n=2, n, p = (1 + Z)*exp(p^2/(1+p)) - 1); Vec(serlaplace(1-1/(1+p)))}

CROSSREFS

A048174 is the case with multiple edges in parallel allowed.

A058379 is the case that order is not significant in series configurations.

Cf. A339289 (unlabeled), A339299, A339301.

Sequence in context: A185085 A201540 A195229 * A296389 A077290 A222780

Adjacent sequences:  A339297 A339298 A339299 * A339301 A339302 A339303

KEYWORD

nonn

AUTHOR

Andrew Howroyd, Dec 22 2020

STATUS

approved

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Last modified July 25 12:56 EDT 2021. Contains 346290 sequences. (Running on oeis4.)