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 A379641 #11 Feb 27 2025 11:06:45
%S A379641 7,3,73,5,31,19,127,17,262657,11,23,37,79,43,631,97,103,87211,32377,
%T A379641 41,92737,67,47,433,601,2731,2593,29,233,18837001,2147483647,193,199,
%U A379641 307,71,246241,223,571,937,61681,13367,77158673929,431,397,271,139,2351,577
%N A379641 Smallest primitive prime factor of 8^n-1.
%C A379641 Also, smallest prime p such that 1/p has octal period n.
%H A379641 Max Alekseyev, <a href="/A379641/b379641.txt">Table of n, a(n) for n = 1..548</a> (first 500 terms from Sean A. Irvine)
%o A379641 (PARI) listap(nn) = {prf = []; for (n=1, nn, vp = (factor(8^n-1)[, 1])~; f = setminus(Set(vp), Set(prf)); prf = concat(prf, f); print1(vecmin(Vec(f)), ", "); ); }
%Y A379641 Cf. A112927 (base 2), A143663 (base 3), A112092 (base 4), A143665 (base 5), A379639 (base 6), A379640 (base 7), A379641 (base 8), A379642 (base 9), A007138 (base 10), A379644 (base 11), A252170 (base 12).
%Y A379641 Cf. A274908.
%K A379641 nonn
%O A379641 1,1
%A A379641 _Sean A. Irvine_, Dec 28 2024