b)
var i, S, n : integer;
begin
write ('Nhap n la:'); readln(n);
S := 0;
for i := 1 to n do S := S + sqr(i);
writeln('Tong la:', S);
readln
end.
c)
var i, n: byte;
S: real;
begin
write ('Nhap n la:'); readln(n);
S := 0;
for i := 1 to n do S := S + 1/i;
writeln('Tong la:', S:3:2);
readln
end.
d)
var i, S, n : integer;
begin
write ('Nhap n la:'); readln(n);
S := 1;
for i := 1 to n do if i mod 2 <> 0 then S := S*i;
writeln('Tich la:', S);
readln
end.
