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 A136699 #7 Aug 01 2015 13:53:40
%S A136699 1,1,2,6,11,3,5,9,7,11,6,1,12,12,12,11,7,2,10,8,4,6,2,7,12,1,2,2,4,12,
%T A136699 9,6,10,5,1,9,12,2,11,7,7,1,3,12,8,9,11,10,12,3,7,6,11,11,9,1,4,7,3,8,
%U A136699 12,4,1,11,2,10,10,7,8,6,4,11,12,5,6,8,10,3,5,5,10,4,3,2,12,6,9,3,4,5,8,4
%N A136699 Final nonzero digit of n! in base 13.
%e A136699 6! = 720 decimal = 435 tridecimal, so a(6) = 5.
%t A136699 f[s_List] := Block[{a = s[[ -1]], len = Length@s}, Append[s, If[Mod[len, 13] == 0, Mod[a*len/13,13], Mod[a*len, 13]]]]; Nest[f, {1}, 100] (* _Robert G. Wilson v_, May 03 2009 *)
%t A136699 f[n_] := Block[{id = IntegerDigits[n!, 13]}, While[id[[ -1]] == 0, id = Most@id]; id[[ -1]]]; Table[ f@n, {n, 0, 100}] (* _Robert G. Wilson v_, May 03 2009 *)
%Y A136699 Cf. A000142, A136690, A136691, A136692, A136693, A136694, A136695, A136696, A008904, A136697, A136698, A136700, A136701, A136702.
%K A136699 base,easy,nonn
%O A136699 0,3
%A A136699 _Carl R. White_, Jan 16 2008