OFFSET
0,6
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
EXAMPLE
a(7) = 5 because 5 binary words of length 7 have at least one subword 1001 and no subwords 11 or 101: 0001001, 0010010, 0100100, 1001000, 1001001.
MAPLE
a:= n-> (Matrix (7, (i, j)-> `if` (i=j-1, 1, `if` (i=7, [-1, 0, -1, 0, 1, -1, 2][j], 0)))^n. <<(0$6), 1>>)[3, 1]: seq (a(n), n=0..50);
MATHEMATICA
CoefficientList[Series[x^4/((x^3+x-1)*(x^4+x-1)), {x, 0, 50}], x] (* G. C. Greubel, Apr 29 2017 *)
PROG
(PARI) x='x+O('x^50); concat([0, 0, 0, 0], Vec(x^4/((x^3+x-1)*(x^4+x-1)))) \\ G. C. Greubel, Apr 29 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 04 2008
STATUS
approved