A091106 a(0)=a(1)=-1. For n>1: a(n)=Sum(i!i^2 Stirling2[n-1,i],i=2,..,n-1).

-1, -1, 0, 8, 78, 764, 8310, 100988, 1362438, 20246444, 328972470, 5805917468, 110645911398, 2265191981324, 49589790516630, 1156201277261948, 28605950745797958, 748605590542359404, 20661245832389468790, 599820758571599742428, 18272940402442730318118

Offset

0,4

Links

Table of n, a(n) for n=0..20.

Formula

E.g.f.: (exp(x)-1)^2/(2(exp(x)-2)^2)-exp(x). a(n)=(1/2)(A069321(n)-A000670(n))-1.

Mathematica

CoefficientList[Series[(1/2)((Exp[x]-1)/(Exp[x]-2))^2-Exp[x], {x, 0, 20}], x]

Crossrefs

Sequence in context: A222191 A240343 A155600 * A199758 A111533 A218499

Adjacent sequences: A091103 A091104 A091105 * A091107 A091108 A091109

Keyword

easy,sign

Author

Mario Catalani (mario.catalani(AT)unito.it), Dec 19 2003

Status

approved