MathLabs

Problem 2

Find an integer nn in the range 100≤n≤1997100\le n\le1997 such that nn divides 2n+22^n+2.
Step 2 of 4: Verify the candidate
946=2⋅11⋅43,2946≡−2(mod946)946=2\cdot11\cdot43,\qquad2^{946}\equiv-2\pmod{946}
Detailed analysis

The compatible candidate in the range is 946=2⋅11⋅43946=2\cdot11\cdot43. Computing modulo each prime-power factor gives 2946≡−2(mod946)2^{946}\equiv-2\pmod{946}, so 946946 divides 2946+22^{946}+2.