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 A220105 #29 Jul 11 2014 14:50:12
%S A220105 0,2,4,8,16,32,15,0,13,12,56,32,40,156,184,0,222,176,58,288,319,464,
%T A220105 392,320,341,496,40,64,30,212,187,0,301,308,9,1040,38,952,472,1088,
%U A220105 944,1544,1076,800,391,508,2069,2048,1191,1312,922,2608,1909,284,2359
%N A220105 2^(n-1) mod n^2.
%C A220105 If p is a Wieferich prime, then a(p) = 1, that is, a(A001220(n)) = 1.
%C A220105 a(n) = 0 iff n = 1 or n = 2^k (k >= 3).
%C A220105 a(n) = 1 iff n is either a Wieferich prime or a Wieferich pseudoprime (i.e. a composite c such that c-1 is in A240719). - _Felix Fröhlich_, Jul 11 2014
%H A220105 T. D. Noe, <a href="/A220105/b220105.txt">Table of n, a(n) for n = 1..10000</a>
%e A220105 a(7) = 2^(7-1) mod 7^2 = 64 mod 49 = 15.
%t A220105 Table[PowerMod[2, n - 1, n^2], {n, 100}] (* _T. D. Noe_, Dec 17 2012 *)
%Y A220105 Cf. A001220, A062173.
%K A220105 nonn
%O A220105 1,2
%A A220105 _Franz Vrabec_, Dec 17 2012