A056333 Number of primitive (aperiodic) reversible string structures with n beads using a maximum of four different colors.

1, 1, 3, 9, 30, 102, 378, 1440, 5607, 22155, 87978, 350775, 1400490, 5597487, 22379145, 89498880, 357952170, 1431737433, 5726775978, 22906819575, 91626580269, 366505186047, 1466017950378, 5864067254880

Offset: 1

Author

Marks R. Nester

Keywords

• nonn

Comments

A string and its reverse are considered to be equivalent. Permuting the colors will not change the 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]

Crossrefs

Cf. A056315.

Formula

Sum mu(d)*A056323(n/d) where d|n.