A056268 Number of primitive (aperiodic) words of length n which contain exactly three different symbols.

0, 0, 6, 36, 150, 534, 1806, 5760, 18144, 55830, 171006, 518580, 1569750, 4732014, 14250450, 42844320, 128746950, 386615376, 1160688606, 3483582660, 10454059938, 31368305694, 94118013006, 282378679920, 847187946000, 2541662931990, 7625194813656, 22875982414740

Offset: 1

Author

Marks R. Nester

Keywords

• nonn

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]

Crossrefs

Cf. A000244, A001117, A008683, A054718.

Programs

PARI

f(n) = 3^n - 3*2^n + 3;
a(n) = sumdiv(n, d, moebius(d)*f(n/d)); \\ Michel Marcus, Mar 25 2022

Formula

a(n) = Sum_{d|n} mu(d)*A001117(n/d).

Extensions

a(11) and following corrected by Georg Fischer, Mar 24 2022