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 A125421 Number of base 9 circular n-digit numbers with adjacent digits differing by 7 or less. 0
 1, 9, 79, 681, 5987, 52649, 463087, 4073225, 35827395, 315131721, 2771845519, 24380686185, 214448408099, 1886252068073, 16591155401263, 145933007686601, 1283602149301635, 11290348248219273, 99308001030865615 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS [Empirical] a(base,n)=a(base-1,n)+F(7) for base>=7.int(n/2)+1 and F(d) is the largest coefficient in (1+x+...+x^(2d))^n LINKS Table of n, a(n) for n=0..18. FORMULA Conjectures from Colin Barker, Jun 02 2017: (Start) G.f.: (1 - x^2 - 14*x^3) / ((1 - x)*(1 - 8*x - 7*x^2)). a(n) = 1 + (4-sqrt(23))^n + (4+sqrt(23))^n for n>0. a(n) = 9*a(n-1) - a(n-2) - 7*a(n-3) for n>3. (End) PROG (S/R) stvar \$[N]:(0..M-1) init \$[]:=0 asgn \$[]->{*} kill +[i in 0..N-1]((\$[i]`-\$[(i+1)mod N]`>7)+(\$[(i+1)mod N]`-\$[i]`>7)) CROSSREFS Sequence in context: A126632 A294344 A125909 * A163445 A190979 A254598 Adjacent sequences: A125418 A125419 A125420 * A125422 A125423 A125424 KEYWORD nonn,base AUTHOR R. H. Hardin, Dec 28 2006 STATUS approved

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Last modified April 22 19:08 EDT 2024. Contains 371906 sequences. (Running on oeis4.)