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 A281071 #13 Jan 23 2017 23:17:21
%S A281071 1,2,1,4,1,6,1,2,1,10,1,4,1,2,1,6,1,6,1,2,1,4,1,4,1,2,1,10,1,6,1,2,1,
%T A281071 4,1,12,1,2,1,8,1,4,1,2,1,6,1,6,1,2,1,4,1,4,1,2,1,6,1,6,1,2,1,4,1,14,
%U A281071 1,2,1,10,1,4,1,2,1,6,1,8,1,2,1,4,1,4,1,2,1,6,1,6,1,2,1,4,1,8,1,2
%N A281071 Largest number k such that b - r is even or r = 0 for all b = 1..k where r = n mod b.
%C A281071 Consider a text mode screen which is a fixed number of character columns wide. Text only breaks at the screen width, there is no manual line break. Then a(n) is the largest screen width in terms of characters so that a string of n printable characters can be perfectly centrally aligned on this and all smaller widths.
%C A281071 a(n) = n for n in {1, 2, 4, 6, 10}, otherwise a(n) < n. The sequence is unbounded.
%H A281071 Martin Janecke, <a href="/A281071/b281071.txt">Table of n, a(n) for n = 1..10000</a>
%e A281071 a(22) = 4 because
%e A281071 22 mod 1 = 0 where r = 0,
%e A281071 22 mod 2 = 0 where r = 0,
%e A281071 22 mod 3 = 1 where 3 - 1 is even,
%e A281071 22 mod 4 = 2 where 4 - 2 is even, but
%e A281071 22 mod 5 = 2 where r > 0 and 5 - 2 is odd.
%o A281071 (PARI) a(n) = {ok = 1; k = 1; while(ok, v = vector(k, b, if ((n % b)==0, 0, b - (n%b))); ok = #select(x->((x % 2)==0), v) == k; if (ok, k++);); k--;} \\ _Michel Marcus_, Jan 23 2017
%Y A281071 Cf. A281072.
%K A281071 easy,nonn
%O A281071 1,2
%A A281071 _Martin Janecke_, Jan 14 2017