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A303874 Number of noncrossing partitions of an n-set up to rotation with all blocks having a prime number of elements. 2

%I #10 May 03 2018 14:51:51

%S 1,0,1,1,1,2,3,5,8,17,37,71,179,366,919,2069,5027,12053,29098,71846,

%T 175485,437438,1087122,2723326,6860525,17301606,43957596,111748571,

%U 285591775,731432424,1879009622,4841510973,12500324496,32366232373,83962263464,218309244314

%N Number of noncrossing partitions of an n-set up to rotation with all blocks having a prime number of elements.

%C The number of such noncrossing partitions counted distinctly is given by A210737.

%H Andrew Howroyd, <a href="/A303874/b303874.txt">Table of n, a(n) for n = 0..500</a>

%o (PARI) \\ number of partitions with restricted block sizes

%o NCPartitionsModCyclic(v)={ my(n=#v);

%o my(p=serreverse(x/(1 + sum(k=1, #v, x^k*v[k])) + O(x^2*x^n) )/x);

%o my(vars=variables(p));

%o my(varpow(r,d)=substvec(r + O(x^(n\d+1)), vars, apply(t->t^d, vars)));

%o my(q=x*deriv(p)/p);

%o my(T=sum(k=1, #v, my(t=v[k]); if(t, x^k*t*sumdiv(k, d, eulerphi(d) * varpow(p,d)^(k/d))/k)));

%o T + 2 + intformal(sum(d=1,n,eulerphi(d)*varpow(q,d))/x) - p

%o }

%o Vec(NCPartitionsModCyclic(vector(40, k, isprime(k))))

%Y Cf. A054357 (unrestricted), A175954 (1 or 2), A210737, A295198, A303875.

%K nonn

%O 0,6

%A _Andrew Howroyd_, May 01 2018

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Last modified April 28 09:05 EDT 2024. Contains 372020 sequences. (Running on oeis4.)