Câu 1 :

uses crt;

var s, i, n : integer;

begin

clrscr;

write('Nhap so n : '); readln(n);

s := 0; for i := 1 to n do

if i mod 2 <> 0 then s := s + i;

write('Tong cac so le = ', s);

readln

end.

Câu 2 :

uses crt;

var snt, n, dem, j : integer;

begin

clrscr;

dem := 0;

write('Nhap so n : '); readln(n);

writeln('Cac so nguyen to be hon hoac bang ', n ,' : ');

for snt := 2 to n do begin

for i := 1 to n do

if snt mod i = 0 then dem := dem + 1;

if dem = 2 then write(snt,'   ');

dem := 0; end;

readln

end.

1)

uses crt;
var n, i, sum: longint;

begin
clrscr;
    readln(n);

    sum:=0;
    for i:=1 to n do
        if i mod 2 = 1 then
            sum:=sum + i;
    
    writeln(sum);
readln;
end.

 

2)

uses crt;
var n, i: longint;

function isPrime(n: longint): boolean;
var i: longint;
begin
    if n < 2 then exit(false);
    for i:=2 to trunc(sqrt(n)) do
        if n mod i = 0 then exit(false);
    exit(true);
end;

begin
clrscr;
    readln(n);

    for i:=1 to n do
        if isPrime(i) then
            write(i, ' ');
readln;
end.