OFFSET
0,7
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
EXAMPLE
a(9) = 6 because 6 binary words of length 8 have at least one subword 10001 and no subwords 11, 101 or 1001: 000010001, 000100010, 001000100, 010001000, 100010000, 100010001.
MAPLE
a:= proc(m) local M;
M:= Matrix (2*m+3, (i, j)-> `if` (i=j-1 and i<>m+1 or j=1 and
i in [1, m+1] or j=m+2 and i in [m+2, 2*m+3], 1, 0));
proc(n) local K; K:= M^(n+m+1); K[m+1, 1] -K[m+2, m+2] end
end(3):
seq (a(n), n=0..55);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 04 2008
STATUS
approved