t0=3 ; t1=50 ;m=4; a[0][t_]=0.8; Do[ loesung=NDSolve[ {y'[t]==2 a[i][t]/(1+a[i][t]^m) - y[t] , y[0]==a[i][t0]}, y, {t,0,t0} ]; a[i+1][t_]=y[t]/.loesung[[1]] , {i,0,Quotient[t1,t0]-1} ]; c[t_]:= a[ Quotient[t,t0] ] [Mod[t,t0]]; bild=ParametricPlot[{c[t],c[t-t0]},{t,2 t0,t1}, PlotRange->All,ImageSize->{400,300}, AxesLabel->{"c(t)","c(t-3)"}];