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A056320
Number of primitive (aperiodic) reversible strings with n beads using exactly four different colors.
1
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]
FORMULA
sum mu(d)*A056311(n/d) where d|n.
CROSSREFS
Cf. A056315.
Sequence in context: A354697 A133386 A305624 * A056311 A009050 A067358
KEYWORD
nonn
STATUS
approved