This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A191546 #14 Feb 17 2020 07:15:29
%S A191546 3,5,7,1201,13421,28393,22796593,15073,163,421,757241,3512477579761,
%T A191546 79,29,24317675453761,136593761,21199857783625129028395239857,37,
%U A191546 2494605276120959,41,43,89,691,97,488700001,53,17713,4201,59,181,2729,449,67,137,71
%N A191546 Smallest prime factor of prime(n)^n + 1 having the form 2*k*n+1.
%H A191546 Amiram Eldar, <a href="/A191546/b191546.txt">Table of n, a(n) for n = 1..82</a>
%e A191546 a(4) = 1201 because prime(4)^4 + 1 = 7^4+1 = 2402 = 2*1201; the prime divisor of the form 2kn + 1 is 1201 = 2*150*4 + 1 with k = 150.
%p A191546 A191546 := proc(n) local ifs,twkn ; ifs := sort(convert(numtheory[factorset]( 1+ithprime(n)^n),list)) ; for twkn in ifs do if (twkn-1) mod (2*n) = 0 then return twkn; end if; end do: return -1 ; end proc: # _R. J. Mathar_, Jun 18 2011
%t A191546 Table[p = First /@ FactorInteger[Prime[n]^n + 1]; Select[p, Mod[#1, n] ==
%t A191546 1 &, 1][[1]], {n, 1, 35}]
%Y A191546 Cf. A069463 (Greatest prime factor of prime(n)^n+1).
%K A191546 nonn
%O A191546 1,1
%A A191546 _Michel Lagneau_, Jun 05 2011