#includeint main(){long a[30] ,i ;a[0] = a[1] = 0 ;a[2] = 1 ;for( i = 3 ; i < 21 ; i ++ )a[i] = a[i-1] + a[i-2] + a[i-3] ;for( i = 0 ; i < 20 ; i ++ ){if( i != 0 && i%5 == 0 )putchar('\n');printf( "%d...