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 A277555 #25 Feb 09 2021 01:54:47
%S A277555 3,8,13,15,18,23,28,33,38,40,43,48,53,58,63,65,68,73,75,78,83,88,90,
%T A277555 93,98,103,108,113,115,118,123,128,133,138,140,143,148,153,158,163,
%U A277555 165,168,173,178,183,188,190,193,198,200,203,208,213,215,218,223,228
%N A277555 Numbers k such that k/5^m == 3 (mod 5), where 5^m is the greatest power of 5 that divides k.
%C A277555 Positions of 3 in A277543. Numbers that have 3 as their rightmost nonzero digit when written in base 5.
%C A277555 This is one sequence in a 4-way splitting of the positive integers; the other three are indicated in the Mathematica program.
%H A277555 Clark Kimberling, <a href="/A277555/b277555.txt">Table of n, a(n) for n = 1..10000</a>
%t A277555 z = 200; a[b_] := Table[Mod[n/b^IntegerExponent[n, b], b], {n, 1, z}]
%t A277555 p[b_, d_] := Flatten[Position[a[b], d]]
%t A277555 p[5, 1] (* A277550 *)
%t A277555 p[5, 2] (* A277551 *)
%t A277555 p[5, 3] (* A277555 *)
%t A277555 p[5, 4] (* A277548 *)
%o A277555 (PARI) isok(n) = n/5^valuation(n, 5) % 5 == 3; \\ _Michel Marcus_, Oct 20 2016
%Y A277555 Cf. A132739, A277543, A277550, A277551, A277548.
%K A277555 nonn,easy
%O A277555 1,1
%A A277555 _Clark Kimberling_, Oct 20 2016