A056319 Number of primitive (aperiodic) reversible strings with n beads using exactly three different colors.

0, 0, 3, 18, 78, 270, 921, 2898, 9147, 27987, 85773, 259557, 785778, 2366892, 7128120, 21425040, 64382550, 193316685, 580372293, 1741819245, 5227115454, 15684238080, 47059266081, 141189599250

Offset: 1

Author

Marks R. Nester

Keywords

• nonn

Comments

Each string and its reverse are considered to be equivalent.

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. A056314.

Formula

Sum mu(d)*A056310(n/d) where d|n.