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 A125734 #16 Apr 15 2024 03:24:18
%S A125734 5,13,37,109,2917,19131877,57395629,16210220612075905069,
%T A125734 3187367866510497232065375864429355521950801431840733951694899540869109890815626195932616388528013,
%U A125734 254244997489062154119688681828370010268347235132197783249391539881181660045297550875174703528321187968562717038040968333
%N A125734 Primes of the form 4*3^k + 1.
%C A125734 Venkataraman showed that, for every p of this form, 3p is a perfect totient number (cf. A082897).
%D A125734 T. Venkataraman, Perfect totient number, The Mathematics Student, Vol. 43 (1975), p. 178. MR0447089.
%H A125734 Amiram Eldar, <a href="/A125734/b125734.txt">Table of n, a(n) for n = 1..14</a>
%H A125734 Paul Loomis, Michael Plytage and John Polhill, <a href="http://www.jstor.org/stable/27646564">Summing up the Euler phi function</a>, The College Mathematics Journal, Vol. 39, No. 1 (Jan. 2008), pp. 34-42 (see Corollary 3).
%F A125734 4*3^k + 1 where k belongs to A005537.
%e A125734 37 = 4*3^2 + 1 is a prime of this form. 973 = 4*3^5 + 1 = 7*139 is not a prime, so is not included in this sequence.
%t A125734 Do[p = 4*3^i + 1; If[PrimeQ@p, Print@p], {i, 0, 300}] (* _Robert G. Wilson v_, Feb 20 2007 *)
%Y A125734 Cf. A005537, A082897.
%K A125734 nonn
%O A125734 1,1
%A A125734 _David Eppstein_, Feb 06 2007, Feb 07 2007
%E A125734 2 more terms from _Robert G. Wilson v_, Feb 20 2007