2.
program phuongt;
uses crt;
  var n, i, s: integer;
begin
       clrscr;
       write('Nhap n = '); readln(n);
       s:=0;
       for i:=4 to n do s:=s+i;
       write('Tong = ', s);
       readln
end.

3.
program phuongt;
uses crt;
  var n, i, s: integer;
begin
       clrscr;
       write('Nhap n = '); readln(n);
       s:=0;
       for i:=1 to n do s:=s+i;
       write('Tong = ', s);
       readln
end.

4.
program phuongt;
uses crt;
  var n, i, s: integer;
begin
       clrscr;
       write('Nhap n = '); readln(n);
       s:=0;
       for i:=4 to n do if i mod 2 <> 0 then s:=s+i;
       write('Tong = ', s);
       readln
end.

5.
program phuongt;
uses crt;
  var n, i, s: integer;
begin
       clrscr;
       write('Nhap n = '); readln(n);
       s:=0;
       for i:=5 to n do if i mod 5 = 0 then s:=s+1;
       write('Co ', s, ' so chia het cho 5');
       readln
end.

6.
program phuongt;
uses crt;
  var n, i, s: integer;
begin
       clrscr;
       write('Nhap n = '); readln(n);
       s:=0;
       for i:=1 to n do if n mod i then s:=s+i;
       write('Tong = ', s);
       readln
end.

7.
program phuongt;
uses crt;
  var n, i, s: integer;
begin
       clrscr;
       write('Nhap n = '); readln(n);
       s:=0;
       for i:=1 to n do if n mod i = 0 then s:=s+1;
       if s=2 then write(n, ' la so nguyen to')
       else
               write(n, ' khong phai so nguyen to');
       readln
end.