#
lfsr:=function(c,k,n)
# c list of coeffs
# k initial values
# n length of resulting sequence
local res,l,i;
res:=ShallowCopy(k);
l:=Length(c);
for i in  [1..n-l] do
Add(res,res{[i..i+l-1]}*c mod 2);
od;
return res;
end;
lfsrlength:=function(v,n)
local i,dets,mat;
dets:=[];
for i in [2..n] do
mat:=List([1..i],x->v{[x..(x-1+i)]}) mod 2;
dets[i]:=Determinant(mat) mod 2;
od;
return dets;
end;
lfsrsolve:=function(v,n)
local mat;
mat:=List([1..n],x->v{[x..(x-1+n)]}) mod 2;
return (v{[n+1..2*n]}*(TransposedMat(mat)^-1 mod 2)) mod 2;
end;