

A056267


Number of primitive (aperiodic) words of length n which contain exactly two different symbols.


4



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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OFFSET

1,2


REFERENCES

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].


LINKS

Table of n, a(n) for n=1..31.


FORMULA

a(n) = Sum_{dn} mu(d)*A000918(n/d), n>0.


PROG

(PARI) a(n) = sumdiv(n, d, moebius(d)*(2^(n/d)  2)); \\ Michel Marcus, Jun 30 2019


CROSSREFS

Cf. A000079, A000918.
A027375 and A038199 are essentially the same sequence with different initial terms.
Sequence in context: A224532 A179674 A038199 * A133996 A284573 A080742
Adjacent sequences: A056264 A056265 A056266 * A056268 A056269 A056270


KEYWORD

nonn


AUTHOR

Marks R. Nester


EXTENSIONS

Corrected and extended by Franklin T. AdamsWatters and T. D. Noe, Oct 25 2006


STATUS

approved



