>>257
これで良いかな?

#include <stdio.h>
void main(void) {
int dan,j,k;
for (dan=1; dan<=9; dan=dan+2){
for(j=1; j<=9-dan; j=j+2){
printf(" ");
}
for(k=1; k<=dan*2-1; k=k+2){
printf("*");
}
printf("\n");
}

for (dan=7; dan>0; dan=dan-2){
for(j=1; j<=9-dan; j=j+2){
printf(" ");
}
for(k=1; k<=dan*2-1; k=k+2){
printf("*");
}
printf("\n");
}
}