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 A138649 #11 Dec 01 2016 07:41:44
%S A138649 0,1,11,91,46,1526,15406,45561,117116,312071,1872426,21000181,
%T A138649 223657336,853662766,5121976596,12421312701,74527876206,141991475986,
%U A138649 2377827762166,18081663838621,32196037719226,2441363034106,491485336407761,2948912018446566
%N A138649 a(n) = 6^n mod 5^n.
%H A138649 Seiichi Manyama, <a href="/A138649/b138649.txt">Table of n, a(n) for n = 0..1430</a>
%t A138649 Table[PowerMod[6,n,5^n],{n,0,30}] (* _Harvey P. Dale_, Jan 23 2014 *)
%Y A138649 Cf. k^n mod (k-1)^n: A002380 (k=3), A064629 (k=4), A138589 (k=5), this sequence (k=6), A139786 (k=7), A138973 (k=8), A139733 (k=9).
%K A138649 nonn
%O A138649 0,3
%A A138649 _N. J. A. Sloane_, May 20 2008