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%I #17 Dec 02 2021 03:11:15
%S 0,1,2,4,11,29,91,286,955,3235,11240,39559,141217,509059,1852248,
%T 6790372,25062536,93043286,347223013,1301777476,4900835727,
%U 18519492431,70220471264,267080436295,1018708832722,3895714521787,14933608764343,57372586025039,220869710184189
%N A simple grammar.
%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=796">Encyclopedia of Combinatorial Structures 796</a>
%F G.f. satisfies A(x) = Sum_{j>=1} (phi(j)/j) * log( 1/(1-B(x^j)) ), where B(x) = x * exp( Sum_{j>=1} (-1)^(j+1) * S(x^j) / j ). - _Sean A. Irvine_, Dec 02 2021
%p spec := [S,{B=Prod(C,Z),C=PowerSet(S),S=Cycle(B)},unlabeled]: seq(combstruct[count](spec,size=n), n=0..20);
%K easy,nonn
%O 0,3
%A encyclopedia(AT)pommard.inria.fr, Jan 25 2000
%E More terms from _Sean A. Irvine_, Dec 02 2021