A191548 Smallest prime factor of prime(n)^n - 1 having the form k*n + 1.

31, 5, 3221, 7, 25646167, 17, 19, 11, 23, 13, 11831, 5839, 31, 17, 137, 19, 751410597400064602523400427092397, 661, 127, 23, 47, 46644217, 101, 79, 2377, 29, 7193, 31, 1310825268269643509279336731098526398390609803239319801398048897, 97, 755569

Offset: 3

Author

Michel Lagneau, Jun 05 2011

Keywords

• nonn

Examples

			a(3) = 31 because prime(3)^3 - 1 = 5^3 - 1 = 124 = 2^2*31; the smallest prime divisor of the form k*n + 1 is 31 = 10*3 + 1 with k = 10.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 3..96

Crossrefs

Cf. A069460 (greatest prime factor of prime(n)^n-1).

Programs

Mathematica

Table[p = First /@ FactorInteger[Prime[n]^n - 1]; Select[p, Mod[#1, n] ==
  1 &, 1][[1]], {n, 3, 30}]