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A124726
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Number of base 27 circular n-digit numbers with adjacent digits differing by 1 or less.
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2
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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
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OFFSET
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0,2
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COMMENTS
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[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
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LINKS
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PROG
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(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))
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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