A339229 Number of oriented series-parallel networks with n integer valued elements spanning an initial interval of positive integers.

1, 5, 46, 677, 13897, 367329, 11875112, 453884998, 20021744482, 1001103144204, 55950350379398, 3456387167052662, 233868854544617505, 17200896572547662922, 1366363690436820691346, 116580486267706011046208, 10633034275200701222560393, 1032398637197381396948606128

Offset: 1

Author

Andrew Howroyd, Nov 28 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) = 5: (11), (12), (21), (1|1), (1|2).
		

Crossrefs

Row sums of A339228.

Programs

PARI

\\ See A339228 for R(n,k).
seq(n)={sum(k=1, n, R(n, k)*sum(r=k, n, binomial(r, k)*(-1)^(r-k)) )}