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A056267
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Number of primitive (aperiodic) words of length n which contain exactly two different symbols.
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4
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0, 2, 6, 12, 30, 54, 126, 240, 504, 990, 2046, 4020, 8190, 16254, 32730, 65280, 131070, 261576, 524286, 1047540, 2097018, 4192254, 8388606, 16772880, 33554400, 67100670, 134217216, 268419060, 536870910, 1073708010, 2147483646
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listen;
history;
text;
internal format)
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OFFSET
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1,2
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REFERENCES
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M. R. Nester, Mathematical investigations of some plant interaction designs, PhD Thesis, University of Queensland, Brisbane, Australia, 1999 [See A056391 for pdf file of Chap. 2].
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LINKS
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FORMULA
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a(n) = Sum_{d|n} mu(d)*A000918(n/d), n>0.
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PROG
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(PARI) a(n) = sumdiv(n, d, moebius(d)*(2^(n/d) - 2)); \\ Michel Marcus, Jun 30 2019
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CROSSREFS
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A027375 and A038199 are essentially the same sequence with different initial terms.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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