Dùng for..to..do:

uses crt;

var i,n: integer;

s: real;

begin

clrscr;

write ('nhap n: ');  readln (n);

s:=0;

for i:=1 to 2*n do s:=s+1/2*i+1;

writeln ('Tong la: ',s:1:2);

readln;

end.

Dùng while..do:

uses crt;

var i,n: integer;

s: real;

begin

clrscr;

write ('nhap n: ');  readln (n);

s:=0;

i:=0;

while i<=2*n do

begin

i:=i+1;

s:=s+1/2*i+1;

end;

writeln ('Tong la: ',s:1:2);

readln;

end.

Cách 1:
uses crt;
var i,n: integer;
    s: real;
begin
clrscr;
    readln(n);
    for i:=1 to n do s:=s+1/(2*n+1);
    write(s:2:3);
    readln
end.
Cách 2:
uses crt;
var i,n: integer;
    s: real;
begin
clrscr;
    readln(n);
    while i<=n do begin
        i:=i+1;
        s:=s+1/(2*n+1);
    end;
    write(s:2:3);
    readln
end.