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A124701 Number of base 8 circular n-digit numbers with adjacent digits differing by 1 or less. 0
1, 8, 22, 50, 130, 338, 904, 2444, 6682, 18410, 51052, 142304, 398380, 1119308, 3154558, 8914010, 25246282, 71644298, 203665054, 579841286, 1653025900, 4718011460, 13479908926, 38548802570, 110327691316, 315985475588 (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, 8) 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,..,8}. 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..25.

FORMULA

G.f.: (1 - 21*x^2 + 28*x^3 + 60*x^4 - 96*x^5 - 15*x^6 + 36*x^7) / ((1 - 2*x)*(1 - 3*x + x^3)*(1 - 3*x + 3*x^3)) (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: A269429 A305181 A048489 * A002968 A211530 A058404

Adjacent sequences:  A124698 A124699 A124700 * A124702 A124703 A124704

KEYWORD

nonn,base

AUTHOR

R. H. Hardin, Dec 28 2006

STATUS

approved

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Last modified January 27 04:57 EST 2020. Contains 331291 sequences. (Running on oeis4.)