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 A055117 #13 Mar 31 2017 22:25:28 %S A055117 0,6,5,4,3,2,1,42,48,47,46,45,44,43,35,41,40,39,38,37,36,28,34,33,32, %T A055117 31,30,29,21,27,26,25,24,23,22,14,20,19,18,17,16,15,7,13,12,11,10,9,8, %U A055117 294,300,299,298,297,296,295,336,342,341,340,339,338,337,329,335,334 %N A055117 Base-7 complement of n (write n in base 7, then replace each digit with its base-7 negative). %H A055117 Alois P. Heinz, <a href="/A055117/b055117.txt">Table of n, a(n) for n = 0..2400</a> %H A055117 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %Y A055117 Cf. A004488, A048647, A055115-A055126. %Y A055117 Column k=7 of A248813. %K A055117 base,easy,nonn %O A055117 0,2 %A A055117 _Henry Bottomley_, Apr 19 2000