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A124726 Number of base 27 circular n-digit numbers with adjacent digits differing by 1 or less. 2
1, 27, 79, 183, 491, 1307, 3583, 9911, 27715, 78051, 221159, 629711, 1800371, 5165187, 14862871, 42878543, 123982195, 359207987, 1042568407, 3030781151, 8823230131, 25719643811, 75061264951, 219298798031, 641338650427 (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, 27) 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,..,27}. See theorem 3.3 in Knopfmacher and others, reference in A124696. - Peter Luschny, Aug 13 2012

LINKS

Table of n, a(n) for n=0..24.

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: A217966 A255186 A121737 * A126381 A129254 A215782

Adjacent sequences:  A124723 A124724 A124725 * A124727 A124728 A124729

KEYWORD

nonn,base

AUTHOR

R. H. Hardin, Dec 28 2006

EXTENSIONS

Edited by Charles R Greathouse IV, Aug 05 2010

STATUS

approved

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Last modified March 24 11:34 EDT 2019. Contains 321448 sequences. (Running on oeis4.)