Identities of the form $397612 = 3^2+9^1+7^6+6^7+1^9+2^3$
A quick Java program reveals the numbers:
- $1$
- $48625$
- $397612$
are the only such numbers which are less than $10^8$. This is not by any means a full answer, but it's a good start. This took a couple minutes to run, so using it to check for higher powers of $n$ isn't viable. Let me know if you have improvements for the code.
My code is below.
import java.util.Arrays;
class WeirdNumberTest
{
public static void main(String args[])
{
for (int number = 1; number < 100000000; number++)
{
int[] digits = getDigits(number);
int sum = 0;
int n = digits.length;
for (int i = 0; i < n; i++)
{
sum += Math.pow(digits[i], digits[n-1-i]);
}
if (number == sum) System.out.println(sum);
}
}
public static int[] getDigits(int n)
{
int nbrDigits = 0;
int currentNbr = n;
while (currentNbr != 0)
{
currentNbr = currentNbr/10;
nbrDigits++;
}
int[] digitArray = new int[nbrDigits];
currentNbr = n;
for (int i = 0; i < nbrDigits; i++)
{
digitArray[i] = currentNbr%10;
currentNbr = currentNbr/10;
}
return digitArray;
}
}
Not quite the same form, but I like $2^59^2 = 2592$.