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

1,3

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]

Links

Table of n, a(n) for n=1..24.

Formula

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

Crossrefs

Cf. A056315.

Sequence in context: A304823 A394948 A317875 * A148948 A148949 A148950

Adjacent sequences: A056330 A056331 A056332 * A056334 A056335 A056336

Keyword

nonn

Author

Marks R. Nester

Status

approved