## H grammiki anadromiki sxesi x(n+3) = (1/2)*x(n+2)-x(n+1)+(1/2)*x(n)
## me arxikes synthikes x(0)=1, x(1)=0, x(2)=2
xx<-{}; y<-2; z<-0; t<-1; n<-40; xx<-c(xx,t); xx<-c(xx,z); xx<-c(xx,y)
for (i in 1:n){ x<-y/2-z+t/2; xx<-c(xx,x); t<-z; z<-y; y<-x}
plot(xx,type="l")

## H grammiki anadromiki sxesi x(n+3) = (9/10)*x(n+2)-x(n+1)+(9/10)*x(n)
## me arxikes synthikes x(0)=1, x(1)=0, x(2)=2
xx<-{}; y<-2; z<-0; t<-1; n<-200; xx<-c(xx,t); xx<-c(xx,z); xx<-c(xx,y)
for (i in 1:n){ x<-9*y/10-z+9*t/10; xx<-c(xx,x); t<-z; z<-y; y<-x}
plot(xx,type="o")