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 A277551 #21 Feb 09 2021 01:54:43
%S A277551 2,7,10,12,17,22,27,32,35,37,42,47,50,52,57,60,62,67,72,77,82,85,87,
%T A277551 92,97,102,107,110,112,117,122,127,132,135,137,142,147,152,157,160,
%U A277551 162,167,172,175,177,182,185,187,192,197,202,207,210,212,217,222,227
%N A277551 Numbers k such that k/5^m == 2 (mod 5), where 5^m is the greatest power of 5 that divides k.
%C A277551 Positions of 2 in A277543. Numbers that have 2 as their rightmost nonzero digit when written in base 5.
%C A277551 This is one sequence in a 4-way splitting of the positive integers; the other three are indicated in the Mathematica program.
%H A277551 Clark Kimberling, <a href="/A277551/b277551.txt">Table of n, a(n) for n = 1..10000</a>
%t A277551 z = 200; a[b_] := Table[Mod[n/b^IntegerExponent[n, b], b], {n, 1, z}]
%t A277551 p[b_, d_] := Flatten[Position[a[b], d]]
%t A277551 p[5, 1] (* A277550 *)
%t A277551 p[5, 2] (* A277551 *)
%t A277551 p[5, 3] (* A277555 *)
%t A277551 p[5, 4] (* A277548 *)
%o A277551 (PARI) isok(n) = n/5^valuation(n, 5) % 5 == 2; \\ _Michel Marcus_, Oct 21 2016
%Y A277551 Cf. A277543, A277550, A277555, A277548.
%K A277551 nonn,easy
%O A277551 1,1
%A A277551 _Clark Kimberling_, Oct 20 2016