Pairs of numbers A256519(n) and S000676(n).
25, 4, 121, 5, 169, 12, 437, 18, 551, 18, 667, 18, 721, 6, 1037, 16, 1159, 18, 1273, 18, 1349, 9, 1403, 18, 1541, 18, 1769, 18, 1943, 18, 2209, 23, 2329, 16, 2363, 16, 2419, 40, 3071, 36, 3713, 23, 4087, 18, 5041, 7, 5111, 9, 7313, 51, 8357, 16, 8479, 16, 9017, 63
1
These numbers are closely related.
T. D. Noe, Plot of 1000 pairs
T. D. Noe, Table of 1000 pairs
(Mma) t2 = {}; Do[If[! PrimeQ[n], mx = FactorInteger[n][[1, 1]]; t = {}; f = 1; Do[f = Mod[k*f, n]; If[f + 1 == n, AppendTo[t, k]], {k, mx - 1}]; If[Length[t] > 0, AppendTo[t2, {n, t}]]], {n, 10^6}]; t2
nonn
T. D. Noe, Jun 19 2015