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 A099638 #5 Oct 15 2013 22:32:35
%S A099638 1,77,7437,741037,74077037,7407437037,740741037037,74074077037037,
%T A099638 7407407437037037,740740741037037037,74074074077037037037,
%U A099638 7407407407437037037037,740740740741037037037037
%N A099638 a[n]=A098210[n]/15.
%C A099638 Patterned-digit obtained when (1,5)-half-repdigit is divided by 15, the least such number.This simple generating rule is often[not always] applicable to provide curious digit-patterns. Thus A=1,B=7 give 111..888 numbers divided by 18 results in A003555.
%F A099638 a[n]=A*(((100^n-1)/9)+B*(10^n - 1)/9)/15, where A=1, B=5-A=4.
%e A099638 n = 20: a[20] = 1111111111111111111155555555555555555555/15 = 74074074074074074077037037037037037037.
%t A099638 f[x_] := 3*((100^x-1)/9) + 4*(10^x-1)/9 Table[f[w], {w, 1, 20}]/15
%Y A099638 Cf. A098210.
%K A099638 nonn
%O A099638 1,2
%A A099638 _Labos Elemer_, Oct 28 2004