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A277671 Number of n-length words over an 8-ary alphabet {a_1,a_2,...,a_8} avoiding consecutive letters a_i, a_{i+1}. 2
1, 8, 57, 406, 2892, 20600, 146736, 1045216, 7445184, 53032832, 377758463, 2690813426, 19166948203, 136528196220, 972504760052, 6927254109472, 49343562590512, 351479407373632, 2503624937520704, 17833584831080448, 127030508108889857, 904851724611169300 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (8,-7,6,-5,4,-3,2,-1)

FORMULA

G.f.: 1/(1 + Sum_{j=1..8} (9-j)*(-x)^j).

MAPLE

a:= proc(n) option remember; `if`(n<0, 0, `if`(n=0, 1,

      -add((-1)^j*(9-j)*a(n-j), j=1..8)))

    end:

seq(a(n), n=0..25);

MATHEMATICA

LinearRecurrence[{8, -7, 6, -5, 4, -3, 2, -1}, {1, 8, 57, 406, 2892, 20600, 146736, 1045216}, 30] (* Harvey P. Dale, May 15 2018 *)

CROSSREFS

Column k=8 of A277666.

Sequence in context: A331792 A097114 A022038 * A015453 A181246 A281355

Adjacent sequences:  A277668 A277669 A277670 * A277672 A277673 A277674

KEYWORD

nonn,easy

AUTHOR

Alois P. Heinz, Oct 26 2016

STATUS

approved

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Last modified December 3 18:19 EST 2021. Contains 349467 sequences. (Running on oeis4.)