A056280 Number of primitive (aperiodic) word structures of length n which contain exactly four different symbols.
0, 0, 0, 1, 10, 65, 350, 1700, 7770, 34095, 145750, 611435, 2532530, 10391395, 42355940, 171797200, 694337290, 2798799150, 11259666950, 45232081795, 181509069700, 727778478075, 2916342574750, 11681056021300, 46771289738800, 187226354413735, 749329038527580
Offset: 1
Keywords
References
- 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]
Links
- Andrew Howroyd, Table of n, a(n) for n = 1..500
Formula
a(n) = Sum_{n > 0, d|n} mu(d)*A000453(n/d).
G.f.: Sum_{k>=1} mu(k) * x^(4*k) / Product_{j=1..4} (1 - j*x^k). - Ilya Gutkovskiy, Apr 15 2021
Extensions
Terms a(25) and beyond from Andrew Howroyd, Apr 15 2021
Comments