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 A197930 #8 Nov 06 2016 08:48:36
%S A197930 1,2,6,10,14,22,26,30,34,38,42,46,58,62,74,78,82,86,94,102,106,110,
%T A197930 114,118,122,134,138,142,146,158,166,170,174,178,182,194,202,206,210,
%U A197930 214,218,222,226,230,254,258,262,266,274,278,282,290,298,302,314,318
%N A197930 Numbers n such that the number of distinct residues in x^(n-1) (mod n), x=0..n-1, equals n.
%C A197930 a(n) = n if n = 2p, p prime > 2, or n = 2q with q nonprime such that q = 1, 15, 21, 39, 51, 55, 57, 69, 85, 87, 91,…
%H A197930 Harvey P. Dale, <a href="/A197930/b197930.txt">Table of n, a(n) for n = 1..1000</a>
%F A197930 n such that A197929(n) = n.
%e A197930 a(8) = 30 because x^29 == 0,1,2, …,28,29 (mod 30) with 30 distinct residues.
%t A197930 lst={}; Table[If[Length[Union[PowerMod[Range[0,n-1],n-1,n]]]==n, AppendTo[lst,n]], {n,320}]; lst
%t A197930 Select[Range[400],Length[Union[PowerMod[Range[0,#-1],#-1,#]]]==#&] (* _Harvey P. Dale_, Nov 06 2016 *)
%Y A197930 Cf. A197929, A195637.
%K A197930 nonn
%O A197930 1,2
%A A197930 _Michel Lagneau_, Oct 19 2011