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 A124851 Number of base 9 circular n-digit numbers with adjacent digits differing by 2 or less. 1

%I

%S 1,9,39,141,587,2479,10731,47063,208547,931047,4180239,18849103,

%T 85269011,386687375,1756855951,7993210831,36405316227,165940691695,

%U 756832203759,3453347063599,15762537566627,71964915505967

%N Number of base 9 circular n-digit numbers with adjacent digits differing by 2 or less.

%C [Empirical] a(base,n)=a(base-1,n)+A005191(n+1) for base>=2.int(n/2)+1

%F G.f.: (1 - 21*x^2 - 14*x^3 + 150*x^4 - 16*x^5 - 150*x^6 + 24*x^7 + 28*x^8) / ((1 + x)*(1 - 4*x + 2*x^2)*(1 - 6*x + 5*x^2 + 8*x^3 - 4*x^4 - 2*x^5)) (conjectured). - _Colin Barker_, Jun 02 2017

%o (S/R) stvar \$[N]:(0..M-1) init \$[]:=0 asgn \$[]->{*} kill +[i in 0..N-1]((\$[i]`-\$[(i+1)mod N]`>2)+(\$[(i+1)mod N]`-\$[i]`>2))

%K nonn,base

%O 0,2

%A _R. H. Hardin_, Dec 28 2006

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Last modified January 24 16:33 EST 2020. Contains 331205 sequences. (Running on oeis4.)