login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A056267 Number of primitive (aperiodic) words of length n which contain exactly two different symbols. 4

%I

%S 0,2,6,12,30,54,126,240,504,990,2046,4020,8190,16254,32730,65280,

%T 131070,261576,524286,1047540,2097018,4192254,8388606,16772880,

%U 33554400,67100670,134217216,268419060,536870910,1073708010,2147483646

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

%D 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].

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

%o (PARI) a(n) = sumdiv(n, d, moebius(d)*(2^(n/d) - 2)); \\ _Michel Marcus_, Jun 30 2019

%Y Cf. A000079, A000918.

%Y A027375 and A038199 are essentially the same sequence with different initial terms.

%K nonn

%O 1,2

%A _Marks R. Nester_

%E Corrected and extended by _Franklin T. Adams-Watters_ and _T. D. Noe_, Oct 25 2006

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 10 16:56 EDT 2020. Contains 336381 sequences. (Running on oeis4.)