看程序写结果：

#include "math.h" #include "stdio.h" int main() { int a1[51] = { 0 }; int i, j, t, t2, n = 50; for ( i = 2; i <= sqrt( n ); i++ ) if ( a1[i] == 0 ) { t2 = n / i; for ( j = 2; j <= t2; j++ ) a1[i * j] = 1; } t = 0; for ( i = 2; i <= n; i++ ) if ( a1[i] == 0 ) { printf( "%4d", i ); t++; if ( t % 10 == 0 ) printf( "\n" ); } printf( "\n" ); }