[Ordinary Differential Equation]
ODESolver[f_,y0_,t0_,t1_,K_]:=
Module[{dt,G,SolList},dt=(t1-t0)/K;
G[{t_,y_}]:={t+dt,y+f[t, y]dt};
SolList=NestList[G,{t0,y0},K];
Interpolation[SolList]]