A323876 Number of labeled graphs on n nodes with three connected components.

0, 0, 1, 6, 55, 825, 20818, 925036, 76321756, 12143833740, 3786364993664, 2323363153263768, 2810644049356050752, 6714880790313869814368, 31734660624638397560681792, 297106568651256947892439231872, 5516820501457062391874183605225216, 203371936690880564729559424288326233856, 14896201998273652941883043518617399703696384

Offset

1,4

References

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, 1973, section 1.2.

Links

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

Marko Riedel et al., Proof of recurrence relation.

Marko Riedel, Maple implementation of memoized recurrence.

Formula

a(n) = A143543(n+1, 3) for n >= 1 and a(0) = 0.

E.g.f.: log(Sum_{q>=0} 2^binomial(q, 2)*z^q/q!)^3/3!.

Crossrefs

Cf. A143543, A323875, A323877.

Sequence in context: A380017 A095652 A132689 * A249672 A255853 A183594

Adjacent sequences: A323873 A323874 A323875 * A323877 A323878 A323879

Keyword

nonn

Author

Marko Riedel, Feb 05 2019

Status

approved