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 A247154 #15 Dec 01 2014 01:45:39
%S A247154 4,3279,22,3279,41542,330805,4,3279,4,1461,142,1812389,1726,3883,4,
%T A247154 3279,4,35,6,1967
%N A247154 a(n) = smallest composite c such that n^(A000010(c)) == 1 (mod c^2), i.e., smallest composite Wieferich number to base n.
%C A247154 a(21) > 10^9
%C A247154 a(22)-a(28): 39, 4, 128165, 4, 9, 22, 9
%C A247154 a(29) > 10^9
%C A247154 a(30)-a(33): 1123787, 4, 3279, 4
%C A247154 a(34) > 10^9
%H A247154 William D. Banks, Florian Luca, Igor E. Shparlinski, <a href="http://dx.doi.org/10.1007/s11139-007-9030-z">Estimates for Wieferich numbers</a>, The Ramanujan Journal, December 2007, Volume 14, Issue 3, pp 361-378.
%H A247154 Takashi Agoh, Karl Dilcher, Ladislav Skula, <a href="http://dx.doi.org/10.1006/jnth.1997.2162">Fermat Quotients for Composite Moduli</a>, Journal of Number Theory, September 1997, Volume 66, Issue 1, pp 29-50.
%o A247154 (PARI) for(n=1, 20, forcomposite(c=1, 1e9, if(Mod(n, c^2)^(eulerphi(c))==1, print1(c, ", "); next({2}))); print1("--, "))
%Y A247154 Cf. A039951, A077816, A241977, A241978, A242958, A242959, A242960, A245529.
%K A247154 nonn,more
%O A247154 1,1
%A A247154 _Felix Fröhlich_, Nov 21 2014