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A056280 Number of primitive (aperiodic) word structures of length n which contain exactly four different symbols. 2

%I

%S 0,0,0,1,10,65,350,1700,7770,34095,145750,611435,2532530,10391395,

%T 42355940,171797200,694337290,2798799150,11259666950,45232081795,

%U 181509069700,727778478075,2916342574750,11681056021300

%N Number of primitive (aperiodic) word structures of length n which contain exactly four different symbols.

%C Permuting the alphabet will not change a word structure. Thus aabc and bbca have the same structure.

%D M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]

%F a(n) = Sum_{n > 0, d|n} mu(d)*A000453(n/d).

%Y Column 4 of A137651.

%Y Cf. A056269.

%K nonn

%O 1,5

%A _Marks R. Nester_

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Last modified September 30 02:36 EDT 2020. Contains 337432 sequences. (Running on oeis4.)