A277669 Number of n-length words over a 6-ary alphabet {a_1,a_2,...,a_6} avoiding consecutive letters a_i, a_{i+1}.

1, 6, 31, 160, 826, 4264, 22012, 113632, 586599, 3028182, 15632291, 80698096, 416585304, 2150525528, 11101591924, 57309407232, 295846593873, 1527239790702, 7884023093755, 40699450421136, 210101523661770, 1084600646648368, 5599000626972168, 28903549078371648

Offset: 0

Author

Alois P. Heinz, Oct 26 2016

Keywords

• nonn
• easy

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (6,-5,4,-3,2,-1)

Crossrefs

Column k=6 of A277666.

Programs

Maple

a:= n-> (<<0|1|0|0|0|0>, <0|0|1|0|0|0>, <0|0|0|1|0|0>,
          <0|0|0|0|1|0>, <0|0|0|0|0|1>, <-1|2|-3|4|-5|6>>^n)[6$2]:
seq(a(n), n=0..30);

Formula

G.f.: 1/(1 + Sum_{j=1..6} (7-j)*(-x)^j).