Let p p p be prime. For the auxiliary equation studied in the paper, let C h A , a B ( p ) C_{h\,A,a\,B}(p) C h A , a B ( p ) denote the number of solutions with the indicated restrictions, and let ϕ \phi ϕ be Euler's totient function. If p − 1 p-1 p − 1 is squarefree, write its prime divisors as q q q ; in general write q α ∥ p − 1 q^\alpha\Vert p-1 q α ∥ p − 1 when q α q^\alpha q α is the exact power of q q q dividing p − 1 p-1 p − 1 .
Auxiliary solution-count conjectures.
C h A N Y , a A N Y ( p ) ≈ ( p − 1 ) + ∑ m ∣ p − 1 ϕ ( m ) m 2 ( ∑ d ∣ ( p − 1 ) / m ϕ ( d m ) d ) 2 . C_{h\,\mathsf{ANY},a\,\mathsf{ANY}}(p)\approx (p-1)+\sum_{m\mid p-1}\frac{\phi(m)}{m^2}\left(\sum_{d\mid (p-1)/m}\frac{\phi(dm)}{d}\right)^2. C h ANY , a ANY ( p ) ≈ ( p − 1 ) + m ∣ p − 1 ∑ m 2 ϕ ( m ) d ∣ ( p − 1 ) / m ∑ d ϕ ( d m ) 2 .
If p − 1 p-1 p − 1 is squarefree, then
C h A N Y , a A N Y ( p ) ≈ ( p − 1 ) + ∏ q ∣ p − 1 ( q + 1 − 1 q ) . C_{h\,\mathsf{ANY},a\,\mathsf{ANY}}(p)\approx (p-1)+\prod_{q\mid p-1}\left(q+1-\frac1q\right). C h ANY , a ANY ( p ) ≈ ( p − 1 ) + q ∣ p − 1 ∏ ( q + 1 − q 1 ) .
In general,
C h A N Y , a A N Y ( p ) ≈ ( p − 1 ) + ∏ q α ∥ p − 1 ( [ ( 1 − 1 q ) α + 1 ] 2 + ( 1 − 1 q ) 3 [ ( α + 1 ) 2 q α + 1 − q q − 1 − 2 ( α + 1 ) α q α + 2 − ( α + 1 ) q α + 1 + q ( q − 1 ) 2 + α 2 q α + 3 − ( 2 α 2 + 2 α − 1 ) q α + 2 + ( α 2 + 2 α + 1 ) q α + 1 − q 2 − q ( q − 1 ) 3 ] ) . C_{h\,\mathsf{ANY},a\,\mathsf{ANY}}(p)\approx (p-1)+\prod_{q^\alpha\Vert p-1}\left(\left[\left(1-\frac1q\right)\alpha+1\right]^2+\left(1-\frac1q\right)^3\left[(\alpha+1)^2\frac{q^{\alpha+1}-q}{q-1}-2(\alpha+1)\frac{\alpha q^{\alpha+2}-(\alpha+1)q^{\alpha+1}+q}{(q-1)^2}+\frac{\alpha^2q^{\alpha+3}-(2\alpha^2+2\alpha-1)q^{\alpha+2}+(\alpha^2+2\alpha+1)q^{\alpha+1}-q^2-q}{(q-1)^3}\right]\right). C h ANY , a ANY ( p ) ≈ ( p − 1 ) + q α ∥ p − 1 ∏ ( [ ( 1 − q 1 ) α + 1 ] 2 + ( 1 − q 1 ) 3 [ ( α + 1 ) 2 q − 1 q α + 1 − q − 2 ( α + 1 ) ( q − 1 ) 2 α q α + 2 − ( α + 1 ) q α + 1 + q + ( q − 1 ) 3 α 2 q α + 3 − ( 2 α 2 + 2 α − 1 ) q α + 2 + ( α 2 + 2 α + 1 ) q α + 1 − q 2 − q ] ) .
The product is over primes q q q dividing p − 1 p-1 p − 1 . Additionally,
C h P R , a A N Y ( p ) ≈ 2 ϕ ( p − 1 ) , C_{h\,\mathsf{PR},a\,\mathsf{ANY}}(p)\approx 2\phi(p-1), C h PR , a ANY ( p ) ≈ 2 ϕ ( p − 1 ) ,
C h A N Y , a P R ( p ) ≈ 2 ϕ ( p − 1 ) , C_{h\,\mathsf{ANY},a\,\mathsf{PR}}(p)\approx 2\phi(p-1), C h ANY , a PR ( p ) ≈ 2 ϕ ( p − 1 ) ,
C h P R , a P R ( p ) ≈ ϕ ( p − 1 ) + ϕ ( p − 1 ) 2 p − 1 . C_{h\,\mathsf{PR},a\,\mathsf{PR}}(p)\approx \phi(p-1)+\frac{\phi(p-1)^2}{p-1}. C h PR , a PR ( p ) ≈ ϕ ( p − 1 ) + p − 1 ϕ ( p − 1 ) 2 .
These predictions are derived from the paper's random-map heuristic for x ↦ x x m o d p x\mapsto x^x\bmod p x ↦ x x mod p and remain conjectural in the supplied text.