OFFSET
0,11
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (2, -1, 0, 0, 0, 0, 0, 1, 0, -1, 0, 0, 0, 0, 0, 0, -1).
FORMULA
G.f.: x^9/((x^8+x-1)*(x^9+x-1)).
a(n) = 2*a(n-1) - a(n-2) + a(n-8) - a(n-10) - a(n-17). - Vincenzo Librandi, Jun 05 2013
EXAMPLE
a(10)=2 because 2 binary words of length 10 have at least one subword 10^{7}1 and no subwords 10^{i}1 with i<7: 0100000001, 1000000010.
MAPLE
a:= n-> coeff(series(x^9/((x^8+x-1)*(x^9+x-1)), x, n+1), x, n):
seq(a(n), n=0..60);
MATHEMATICA
CoefficientList[Series[x^9 / ((x^8 + x - 1) (x^9 + x - 1)), {x, 0, 60}], x] (* Vincenzo Librandi, Jun 04 2013 *)
PROG
(Magma) [n le 9 select 0 else n le 17 select n-9 else 2*Self(n-1)-Self(n-2) +Self(n-8)-Self(n-10)-Self(n-17): n in [1..60]]; // Vincenzo Librandi, Jun 05 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Aug 04 2008
STATUS
approved