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 A218584 #11 Mar 05 2013 00:51:27 %S A218584 1,3,5,7,9,13,15,21,27,35,39,45,63,65,81,91,105,117,135,169,189,195, %T A218584 273,315,351,405,455,507,567,585,819,845,945,1053,1183,1365,1521,1701, %U A218584 1755,2457,2535,2835,3159,3549,4095,4563,5265,5915,7371,7605,8505,10647 %N A218584 Numbers n such that 2^A000010(n*x) == 1 (mod (n*x)^2), where x = 3837523 is the product of the first 2 Wieferich primes 1093 and 3511. %C A218584 3837523*a(n) is a term in A077816. %C A218584 If this sequence is finite, then there are finitely many Wieferich primes (A001220). %H A218584 Arkadiusz Wesolowski, <a href="/A218584/b218584.txt">Table of n, a(n) for n = 1..74</a> %t A218584 x = 3837523; Select[Range[1, 10647, 2], PowerMod[2, EulerPhi[#*x], (#*x)^2] == 1 &] %o A218584 (PARI) is(n)=Mod(2,(3837523*n)^2)^eulerphi(3837523*n)==1 \\ _Charles R Greathouse IV_, Mar 05 2013 %Y A218584 Cf. A001220, A077816. %K A218584 nonn %O A218584 1,2 %A A218584 _Arkadiusz Wesolowski_, Nov 03 2012