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%I #11 Jul 18 2017 07:58:49
%S 1,13,157,1813,21997,267483,3255907,39636855,482546341,5874634345,
%T 71519267407,870693584543,10600043444419,129047604857977,
%U 1571058121063511,19126458200814873,232850330879455797
%N Number of base 13 circular n-digit numbers with adjacent digits differing by 9 or less.
%C [Empirical] a(base,n)=a(base-1,n)+F(9) for base>=9.int(n/2)+1 and F(d) is the largest coefficient in (1+x+...+x^(2d))^n.
%F G.f.: (1-6*x^2-100*x^3+15*x^4+148*x^5-5*x^6-42*x^7) / ((1-2*x-x^2+x^3)*(1-11*x-15*x^2+8*x^3+7*x^4)) (conjectured). - _Colin Barker_, Jul 18 2017
%o (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-1](($[i]`-$[(i+1)mod N]`>9)+($[(i+1)mod N]`-$[i]`>9))
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 28 2006
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