Questions On Turning Thirty-One, part II by KlionskyG

MATH
Last one!
31 can be written in the form (n^k - 1) for integers n and k greater than 1.

All in one string of numerals, write out 31 (base 10) in base n and then base k.

("987654321" is one string of numerals; "9876 and 54,321" is not.)