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A211311 a(n) = number |fdw(P,(n))| of entangled P-words with s=4. 0

%I

%S 1,68,34236,62758896,304863598320,3242854167461280,

%T 66429116436728636640,2389384600126093124110080

%N a(n) = number |fdw(P,(n))| of entangled P-words with s=4.

%C See Jenca and Sarkoci for the precise definition.

%H Gejza Jenca and Peter Sarkoci, <a href="http://arxiv.org/abs/1112.5782">Linear extensions and order-preserving poset partitions</a>, arXiv preprint arXiv:1112.5782, 2011

%F From Peter Bala, Sep 05 2012: (Start)

%F Conjectural e.g.f.: 2 - 1/A(x), where A(x) = sum {n = 0..inf} (4*n)!/24^n*x^n/n! is the e.g.f. for A014608 (also the o.g.f. for A025036).

%F If true, this leads to the recurrence equation: a(n) = (4*n)!/24^n - sum {k = 1..n-1} (4*k)!/24^k*binomial(n,k)*a(n-k) with a(1) = 1.

%F (End)

%Y Cf. A014608, A025036.

%K nonn

%O 1,2

%A _N. J. A. Sloane_, Apr 08 2012

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Last modified August 4 14:11 EDT 2020. Contains 336201 sequences. (Running on oeis4.)