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

1,4

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]

Links

Table of n, a(n) for n=1..22.

Formula

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

Crossrefs

Cf. A056315.

Sequence in context: A354697 A133386 A305624 * A056311 A009050 A067358

Adjacent sequences: A056317 A056318 A056319 * A056321 A056322 A056323

Keyword

nonn

Author

Marks R. Nester

Status

approved