OFFSET
0,13
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (2,-1,0,0,0,0,0,0,0,1,0,-1,0,0,0,0,0,0,0,0,-1).
FORMULA
G.f.: x^11/((x^10+x-1)*(x^11+x-1)).
a(n) = 2*a(n-1) -a(n-2) +a(n-10) -a(n-12) -a(n-21). - Vincenzo Librandi, Jun 05 2013
EXAMPLE
a(12)=2 because 2 binary words of length 12 have at least one subword 10^{9}1 and no subwords 10^{i}1 with i<9: 010000000001, 100000000010.
MAPLE
a:= n-> coeff(series(x^11/((x^10+x-1)*(x^11+x-1)), x, n+1), x, n):
seq(a(n), n=0..60);
MATHEMATICA
CoefficientList[Series[x^11 / ((x^10 + x - 1) (x^11 + x - 1)), {x, 0, 60}], x] (* Vincenzo Librandi, Jun 05 2013 *)
PROG
(Magma) [n le 11 select 0 else n le 21 select n-11 else 2*Self(n-1)-Self(n-2) +Self(n-10)-Self(n-12)-Self(n-21): n in [1..60]]; // Vincenzo Librandi, Jun 05 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Aug 04 2008
STATUS
approved