打印特殊矩阵，具体要求如下：打印9*9阶的方阵，要求最外圈的均是1，次外圈的均是2，照此规律方阵,要求从键盘输入任意一个数，输出题中要求的
特殊方阵
如果是5，则特殊方阵的形式为：1 1 1 1 1 1 1 1 1
                             1 2 2 2 2 2 2 2 1
                             1 2 3 3 3 3 3 2 1
                             1 2 3 4 4 4 3 2 1
                             1 2 3 4 5 4 3 2 1
                             1 2 3 4 4 4 3 2 1
                             1 2 3 3 3 3 3 2 1
                             1 2 2 2 2 2 2 2 1
                             1 1 1 1 1 1 1 1 1
                                                      
#include<stdio.h>
int main(void)
{
    int n,**a,i,j;
    printf("please input a integer number(n>0):");
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        for(j=i;j<=2*n-i;j++)
        {
            *(*(a+i)+j)=i;//a[i][j]=i;
            *(*(a+2*n-i)+j)=i;//a[2*n-i][j]=i;
            *(*(a+j)+i)=i;//a[j][i]=i;
            *(*(a+2*n-j)+i)=i;//a[2*n-j][i]=i;
        }
        for(i=1;i<=2*n-1;i++)
        {
            for(j=1;j<=2*n-1;j++)
                printf("%d ",*(*(a+i)+j));
            putchar('\n');
        }
}
:\Users\Administrator\Desktop\8.c(11) : warning C4700: local variable 'a' used without having been initialized
输出结果不对，不知道哪里出错，请各位不吝赐教

#include<stdio.h>
int main(void)
{
    int n,a[2*n-1][2*n-1],i,j;
    printf("please input a integer number(n>0):");
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        for(j=i;j<=2*n-i;j++)
        {
            a[i][j]=i;
            a[2*n-i][j]=i;
            a[j][i]=i;
                a[2*n-j][i]=i;
        }
        for(i=1;i<=2*n-1;i++)
        {
            for(j=1;j<=2*n-1;j++)
                printf("%d ",a[i][j]);
            putchar('\n');
        }
}
则会出现a数组大小未知的错误，那么到底该如何写才能使a数组的大小已知且输入任意的数n呢