Adesso è così:
int main()
{
int N1;
N1 = 2;
For(N1<=50;
{printf("%d\n" ,N1);
N1=N1+2}

}
ma ho sempre 2 errori...

C:\Documents and Settings\Elricmarci\Desktop\Main\main.c|8|error: syntax error before ';' token|
C:\Documents and Settings\Elricmarci\Desktop\Main\main.c|10|error: syntax error before '}' token|
||=== Build finished: 2 errors, 1 warnings ===|