

A124719


Number of base 26 circular ndigit numbers with adjacent digits differing by 1 or less.


1



1, 26, 76, 176, 472, 1256, 3442, 9518, 26608, 74912, 212206, 604058, 1726582, 4952246, 14246644, 41090936, 118785568, 344073056, 998415598, 2901784298, 8445850762, 24614293082, 71820129424, 209785569908, 613390314046
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OFFSET

0,2


COMMENTS

[Empirical] a(base,n)=a(base1,n)+A002426(n+1) for base>=1.int(n/2)+1
a(n) = T(n, 26) 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,..,26}. See theorem 3.3 in Knopfmacher and others, reference in A124696.  Peter Luschny, Aug 13 2012


LINKS



PROG

(S/R) stvar $[N]:(0..M1) init $[]:=0 asgn $[]>{*} kill +[i in 0..N1](($[i]`$[(i+1)mod N]`>1)+($[(i+1)mod N]`$[i]`>1))


CROSSREFS



KEYWORD

nonn,base


AUTHOR



STATUS

approved



