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 A056212 #17 Jun 29 2021 05:55:05
%S A056212 211,617,1499,2087,2857,6007,6469,7127,7211,7589,9661,10193,13259,
%T A056212 13553,14771,18047,18257,19937,20903,21379,23549,26153,27259,27539,
%U A056212 32299,33181,33461,34847,35491,35897,41651,42407,42491,43051,43793
%N A056212 Primes p whose period of reciprocal equals (p-1)/7.
%C A056212 Cyclic numbers of the seventh degree (or seventh order): the reciprocals of these numbers belong to one of seven different cycles. Each cycle has the (number minus 1)/7 digits.
%H A056212 Amiram Eldar, <a href="/A056212/b056212.txt">Table of n, a(n) for n = 1..10000</a>
%H A056212 <a href="/index/1#1overn">Index entries for sequences related to decimal expansion of 1/n</a>
%t A056212 f[n_Integer] := Block[{ds = Divisors[n - 1]}, (n - 1)/Take[ ds, Position[ PowerMod[ 10, ds, n], 1] [[1, 1]]] [[ -1]]]; Select[ Prime[ Range[4, 4700]], f[ # ] == 7 &]
%Y A056212 Cf. A097443, A055628, A056157, A056210, A056211, A056213, A056214, A056215, A056216, A056217, A098680, A135073.
%K A056212 nonn,base
%O A056212 1,1
%A A056212 _Robert G. Wilson v_, Aug 02 2000
%E A056212 Edited by _N. J. A. Sloane_, Apr 30 2007