A052826 A simple grammar: product of cycles and cycles of cycles.

0, 0, 2, 9, 48, 315, 2497, 23394, 254132, 3149826, 43945354, 682314028, 11676044036, 218402171520, 4433885571840, 97098961376112, 2281563329170752, 57255174735315792, 1528204674443305680, 43227315891291907488, 1291646719998952196448, 40652195494651491747840

Offset: 0

Author

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

Keywords

• easy
• nonn

Links

• INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 791

Programs

Maple

spec := [S,{B=Cycle(C),C=Cycle(Z),S=Prod(C,B)},labeled]: seq(combstruct[count](spec,size=n), n=0..20);

Formula

E.g.f.: log(-1/(-1+x))*log(-1/(-1+log(-1/(-1+x)))).

Extensions

More terms from Alois P. Heinz, Mar 16 2016