OFFSET
1,6
COMMENTS
Permuting the alphabet will not change a word structure. Thus aabc and bbca have the same structure.
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]
FORMULA
a(n) = Sum_{n > 0, d|n} mu(d)*A000481(n/d).
G.f.: Sum_{k>=1} mu(k) * x^(5*k) / Product_{j=1..5} (1 - j*x^k). - Ilya Gutkovskiy, Apr 15 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved