MathCastle
Number TheorySuperchallengeOrders and Primitive Roots

Orders and Primitive Roots · Superchallenge problem

Modulo the prime 6161, call aa (with 1≤a≤601 \le a \le 60) a kk-th power if xk≡a(mod61)x^k \equiv a \pmod{61} has a solution. For how many aa with 1≤a≤601 \le a \le 60 is aa a kk-th power for exactly two of the four values k=2,3,4,5k = 2, 3, 4, 5?