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 A128357 #10 Jun 11 2021 09:46:35
%S A128357 10,7,311,127,23,157,343927,7805561,47,9629,311,25679,821,1470086279,
%T A128357 12409,71233,1232333,2443783,2939291,71711,352883,181113265579,167,
%U A128357 105199,3881,1314520253,619,20759,117503,1162660843,1880415721,263
%N A128357 Quotients A128356(n)/prime(n).
%C A128357 A128356 = {20, 21, 1555, 889, 253, 2041, 5846759, ...} = Least number k>1 (that is not the power of prime p) such that k divides (p+1)^k-1, where p = prime(n). Most listed terms are primes, except a(7) = 20231*17 and a(8) = 410819*19. a(15) = 12409. a(16) = 71233.
%C A128357 Note that all prime listed terms of {a(n)} coincide with terms of A128456 = {2, 7, 311, 127, 23, 157, 7563707819165039903, 75368484119, 47, 9629, 311, 25679, 821, ...} = least prime factor of ((p+1)^p - 1)/p^2, where p = prime(n).
%Y A128357 Cf. A128356 (least number k > 1 (that is not a power of prime p) such that k divides (p+1)^k-1, where p = prime(n)).
%Y A128357 Cf. A014960, A128360, A128358, A014960, A014956, A014951, A014949, A014946, A014945, A067945.
%Y A128357 Cf. A128456 (least prime factor of ((p+1)^p - 1)/p^2, where p = prime(n)).
%K A128357 hard,nonn
%O A128357 1,1
%A A128357 _Alexander Adamchuk_, Mar 02 2007, Mar 09 2007
%E A128357 Terms a(14) onwards from _Max Alekseyev_, Feb 08 2010