A056320 Number of primitive (aperiodic) reversible strings with n beads using exactly four different colors.

0, 0, 0, 12, 120, 780, 4212, 20412, 93360, 409260, 1749780, 7338000, 30394560, 124700928, 508291692, 2061586800, 8332140720, 33585682920, 135116412660, 542785390680, 2178110585388, 8733343485120

Offset: 1

Author

Marks R. Nester

Keywords

• nonn

Comments

A 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. A056315.

Formula

sum mu(d)*A056311(n/d) where d|n.