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 A277543 #14 Oct 26 2016 15:23:57
%S A277543 1,2,3,4,1,1,2,3,4,2,1,2,3,4,3,1,2,3,4,4,1,2,3,4,1,1,2,3,4,1,1,2,3,4,
%T A277543 2,1,2,3,4,3,1,2,3,4,4,1,2,3,4,2,1,2,3,4,1,1,2,3,4,2,1,2,3,4,3,1,2,3,
%U A277543 4,4,1,2,3,4,3,1,2,3,4,1,1,2,3,4,2,1
%N A277543 a(n) = n/5^m mod 5, where 5^m is the greatest power of 5 that divides n.
%C A277543 a(n) is the rightmost nonzero digit in the base 5 expansion of n (A007091).
%H A277543 Clark Kimberling, <a href="/A277543/b277543.txt">Table of n, a(n) for n = 1..10000</a>
%F A277543 a(n) = A132739(n) mod 5 = A010874(A132739(n)). - _Michel Marcus_, Oct 20 2016
%e A277543 a(20) = (20/5 mod 5) = 4.
%t A277543 Table[Mod[n/5^IntegerExponent[n, 5], 5], {n, 1, 160}]
%o A277543 (PARI) a(n) = n/5^valuation(n, 5) % 5; \\ _Michel Marcus_, Oct 20 2016
%Y A277543 Cf. A007091, A010874, A132739.
%Y A277543 Cf. A277550, A277551, A277555, A277548 (positions of 1, 2, 3 and 4 in this sequence).
%K A277543 nonn,easy
%O A277543 1,2
%A A277543 _Clark Kimberling_, Oct 19 2016