Suma div: suma(1->nr_prime) ( nr_prim^(putere+1)-1 ) / nr_prim-1

PASCAL:

program ciurul_lui_Eratostene;
var prim:array[2..1000000] of boolean;
    nr,i,j:longint;
    f:text;
begin
assign(f,'ciur.in');
reset(f);
readln(f,nr);
close(f);
i := 4;
while (i <= nr) do 
  begin
    Prim[i] = false;
    i := i + 2;
  end;
i := 3;
while (i * i <= nr) do 
  begin
    if (Prim[i] = true) then 
      begin
         j = i * i;
        while (j <= nr) do 
          begin
            Prim[j] = false;
            j := j + i;
          end;
       end;
  end;
end.

C++:

1)

i=2;
while (i*i<=x) 
{
	if (!Prim[i2]) 
	{
		j=i*i;
		while (j<=x) 
		{
			Prim[j]=true;
			j+=i;
		}
	}
	i2++;
}

2)

for(register int i=3;i<=val;i+=2)
		if(!Prim[i])
			for(register int j=2;j*i<=val;++j)
				Prim[i*j]=true;