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A056274
Number of primitive (aperiodic) word structures of length n using a 3-ary alphabet.
1
1, 1, 4, 12, 40, 116, 364, 1080, 3276, 9800, 29524, 88440, 265720, 796796, 2391440, 7173360, 21523360, 64566684, 193710244, 581120880, 1743391832, 5230147076, 15690529804, 47071499760, 141214768200
OFFSET
1,3
COMMENTS
Permuting the alphabet will not change a word structure. Thus aabc and bbca have the same 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]
FORMULA
Sum mu(d)*A007051(n/d-1) where d|n and n>0.
CROSSREFS
Cf. A054718.
Sequence in context: A344122 A328533 A265127 * A335806 A058353 A104525
KEYWORD
nonn
STATUS
approved