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 A084738 #26 Mar 17 2023 09:56:12
%S A084738 3,13,5,31,7,2801,73,0,11,50544702849929377,13,30941,211,241,17,307,
%T A084738 19,109912203092239643840221,421,463,23,292561,601,0,321272407,757,29,
%U A084738 732541,31,917087137,0,1123,2458736461986831391
%N A084738 Smallest prime of the form (n^k-1)/(n-1), or 0 if no such prime exists.
%C A084738 As mentioned by Dubner, when n is a power (greater than 1) of a prime, then (n^k-1)/(n-1) will usually be composite for all k, which is the case for n = 9, 25, 32 and 49. - _T. D. Noe_, Jan 23 2004
%C A084738 Here, a(n) is the smallest prime of the form (n^k-1)/(n-1) with k >= 2 while in A285642 it is the smallest prime with k > 2. Differences occur when (n^2-1)/(n-1) = n+1 is prime, and therefore, when n = prime(m) - 1 is in A006093 (see formula). - _Bernard Schott_, Mar 16 2023
%H A084738 H. Dubner, <a href="http://dx.doi.org/10.1090/S0025-5718-1993-1185243-9">Generalized repunit primes</a>, Math. Comp., 61 (1993), 927-930.
%F A084738 a(A006093(n)) = prime(n) for n >=2. - _Bernard Schott_, Mar 16 2023
%e A084738 a(8) = 73 = (8^3-1)/(8-1).
%t A084738 Table[SelectFirst[(n^# - 1)/(n - 1) & /@ Range[10^3], PrimeQ] /. k_ /; MissingQ@ k -> 0, {n, 2, 34}] (* _Michael De Vlieger_, Apr 24 2017, Version 10.2 *)
%Y A084738 Cf. A076481.
%Y A084738 Cf. A084740 (least k such that (n^k-1)/(n-1) is prime).
%Y A084738 Cf. A006093, A285642.
%K A084738 nonn
%O A084738 2,1
%A A084738 _Amarnath Murthy_ and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Jun 15 2003
%E A084738 More terms from _T. D. Noe_, Jan 23 2004