A340028 Number of unlabeled 2-connected graphs with n vertices rooted at a pair of noninterchangeable vertices.

0, 1, 1, 7, 55, 655, 11147, 287791, 11787747, 804475261, 94875366649, 19825870580671, 7466490852631207, 5129453728126116131, 6487332587944013948099, 15213161506747424007012971, 66536415576917924594383104139, 545371527333985035460963541248785

Offset: 1

Author

Andrew Howroyd, Jan 02 2021

Keywords

• nonn

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..30

Crossrefs

Cf. A002218, A004115, A241768, A304070, A304074, A340029.

Programs

PARI

\\ See A004115 for graphsSeries and A339645 for combinatorial species functions.
cycleIndexSeries(n)={my(g=graphsSeries(n), gcr=sPoint(g)/g); x*sPoint(sSolve( sLog( gcr/(x*sv(1)) ), gcr ))}
{ my(N=15); Vec(OgfSeries(cycleIndexSeries(N)), -N) }