[B][COLOR="Blue"]Uses crt;
var i, n: integer;
tong: real;
begin
clrscr;
write ('Nhap so N la so chan: '); readln (n);
if n mod 2 <>0 then
begin
write ('So ban nhap khong phai la so chan! An Enter va chay lai!');
readln; exit;
end;
i:=1;
while i<=n+1 do
begin
tong:=tong+1/i;
i:=i+2;
end;
write ('Tong S la ',tong:0:4);
readln
end.[/COLOR][/B]
3/ tính tổng s=1/1^2+1/2^2+..+1/n^2
uses crt;
var s:real;i,n:integer;
begin clrscr;
write('Nhap n:');readln(n);
s:=0;
for i:=1 to n do
s:=s+1/sqr(i);
writeln('Tong S la:',s:0:5);
readln
end.