%I #13 Aug 10 2020 22:21:52

%S 0,1,2,5,16,56,221,900,3839,16752,74701,338327,1553181,7208191,

%T 33768389,159463655,758291989,3627890869,17450572584,84342086908,

%U 409394388458,1994883122360,9754673396640,47850963112328,235413886888082,1161267995487057,5742484341773444

%N Number of objects generated by the Combstruct grammar defined in the Maple program. See the link for the grammar specification.

%H Andrew Howroyd, <a href="/A052815/b052815.txt">Table of n, a(n) for n = 0..200</a>

%H C. G. Bower, <a href="/transforms2.html">Transforms (2)</a>.

%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=780">Encyclopedia of Combinatorial Structures 780</a>

%H Maplesoft, <a href="https://www.maplesoft.com/support/help/Maple/view.aspx?path=examples%2fcombstruct_grammars">Combstruct grammars</a>.

%F G.f.: 1 - x/g(x) where g(x) is the g.f. of A052818. - _Andrew Howroyd_, Aug 10 2020

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

%o (PARI) \\ CIK (necklace, indistinct, unlabeled) in Transforms (2).

%o CIK(p,n)={sum(d=1, n, eulerphi(d)/d*log(subst(1/(1+O(x*x^(n\d))-p), x, x^d)))}

%o seq(n)={my(p=O(x)); for(n=1, n, p=CIK(x/(1-p), n)); Vec(p, -(n+1))} \\ _Andrew Howroyd_, Aug 10 2020

%Y Cf. A052818.

%K easy,nonn

%O 0,3

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

%E Terms a(21) and beyond from _Andrew Howroyd_, Aug 10 2020