A218696 Number of components over all graphs on n labeled nodes with unicyclic components (graphs counted by A137916).

1, 15, 222, 3680, 69345, 1477182, 35234220, 932070708, 27109785510, 860394764515, 29600058300780, 1097511032533500, 43637308561557074, 1852311640075120980, 83612841417061582320, 3999611090385007608840, 202111299843794061251580, 10758947714752854861908379

Offset

3,2

Links

Alois P. Heinz, Table of n, a(n) for n = 3..150

Formula

a(n) = Sum_{m=1..floor(n/3)} A106239(n,m)*m.

Mathematica

nn=22; t=Sum[n^(n-1)x^n/n!, {n, 1, nn}]; Drop[Range[0, nn]!CoefficientList[ Series[D[Exp[y(Log[1/(1-t)]/2-t/2-t^2/4)], y]/.y->1, {x, 0, nn}], x], 3]

Crossrefs

Cf. A057500.

Sequence in context: A279530 A057500 A137916 * A367863 A297669 A171320

Adjacent sequences: A218693 A218694 A218695 * A218697 A218698 A218699

Keyword

nonn

Author

Geoffrey Critzer, Nov 04 2012

Status

approved