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A056319
Number of primitive (aperiodic) reversible strings with n beads using exactly three different colors.
1
0, 0, 3, 18, 78, 270, 921, 2898, 9147, 27987, 85773, 259557, 785778, 2366892, 7128120, 21425040, 64382550, 193316685, 580372293, 1741819245, 5227115454, 15684238080, 47059266081, 141189599250
OFFSET
1,3
COMMENTS
Each 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)*A056310(n/d) where d|n.
CROSSREFS
Cf. A056314.
Sequence in context: A245580 A043008 A241628 * A056310 A309259 A308853
KEYWORD
nonn
STATUS
approved