login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A124700 Number of base 7 circular n-digit numbers with adjacent digits differing by 1 or less. 1
1, 7, 19, 43, 111, 287, 763, 2051, 5575, 15271, 42099, 116651, 324591, 906367, 2538331, 7126403, 20049671, 56509639, 159514963, 450865067, 1275778031, 3613401695, 10242581819, 29053799555, 82461727687, 234163952487 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
[Empirical] a(base,n)=a(base-1,n)+A002426(n+1) for base>=1.int(n/2)+1.
a(n) = T(n, 7) where T(n, k) = Sum_{j=1..k} (1+2*cos(j*Pi/(k+1)))^n. These are the number of smooth cyclic words of length n over the alphabet {1,2,..,7}. See theorem 3.3 in Knopfmacher and others, reference in A124696. - Peter Luschny, Aug 13 2012
LINKS
FORMULA
G.f.: (1 - 2*x)*(1 + 2*x - 11*x^2 - 12*x^3 + 21*x^4 + 6*x^5 - 3*x^6) / ((1 - x)*(1 - 2*x - x^2)*(1 - 4*x + 2*x^2 + 4*x^3 - x^4)) (conjectured). - Colin Barker, Jun 03 2017
PROG
(S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-1](($[i]`-$[(i+1)mod N]`>1)+($[(i+1)mod N]`-$[i]`>1))
CROSSREFS
Sequence in context: A268801 A155275 A155268 * A155336 A155427 A155403
KEYWORD
nonn,base
AUTHOR
R. H. Hardin, Dec 28 2006
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 05:39 EDT 2024. Contains 371235 sequences. (Running on oeis4.)