A218378 Number of simple labeled graphs on n nodes with all odd size components.

1, 1, 1, 5, 17, 769, 4609, 1882805, 15138593, 66365067361, 664157177281, 35645315131333445, 427773958289546417, 301274983519644591252769, 4217875813061550908307649, 40527712572140444650575170520245, 648443738687003872454538321727553

Offset

0,4

Links

Table of n, a(n) for n=0..16.

Formula

E.g.f.: exp( (A(x) - A(-x))/2 ) where A(x) is the e.g.f. for A001187.

Mathematica

nn=21; a=Sum[2^Binomial[n, 2]x^n/n!, {n, 0, nn}]; c=Range[0, nn]! CoefficientList[Series[ Log[a]+1, {x, 0, nn}], x]; cox= Sum[c[[i]]x^(i-1)/(i-1)!, {i, 2, nn, 2}]; Select[Range[0, nn]! CoefficientList[Series[Exp[cox], {x, 0, nn}], x], #>0&]

Crossrefs

Cf. A218377, A182124.

Sequence in context: A070294 A377779 A245568 * A119531 A248921 A172996

Adjacent sequences: A218375 A218376 A218377 * A218379 A218380 A218381

Keyword

nonn

Author

Geoffrey Critzer, Oct 27 2012

Status

approved