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

Author

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

Keywords

• easy
• sign

Programs

Mathematica

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

Formula

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