
term(x,i):=((-1)^i)*(x^(2*i+1))/(2*i+1);

atn(x):=N(Sum(i,0,20,term(x,i)));

pi():=N(Sum(i,0,5,16*term(0.2,i)-4*term(1.0/239,i)));

Function("tst",{})
    [
     Local(res,t1,t2,i,l,ll,dum);
     res:=0;
     t1:= -5;
     t2:= -239;
     l:=1.0/57121;
     ll:= -1;
     dum:=1;
     i:=0;
     While(dum > 0.000000000000000000000000001 Or
           dum < -0.000000000000000000000000001)
     [
     t1:= -t1*0.04;
     t2:= -t2*l;
 ll:=ll+2;
 dum:=(16*t1-4*t2)/ll;

res:=res+dum;
     i++;
     ];
     res;
    ];

