A056267 Number of primitive (aperiodic) words of length n which contain exactly two different symbols.

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

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_{d|n} 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 * A348412 A133996 A284573

Adjacent sequences: A056264 A056265 A056266 * A056268 A056269 A056270

Keyword

nonn

Author

Marks R. Nester

Extensions

Corrected and extended by Franklin T. Adams-Watters and T. D. Noe, Oct 25 2006

Status

approved