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 A055121 #12 Mar 31 2017 22:22:49 %S A055121 0,10,9,8,7,6,5,4,3,2,1,110,120,119,118,117,116,115,114,113,112,111, %T A055121 99,109,108,107,106,105,104,103,102,101,100,88,98,97,96,95,94,93,92, %U A055121 91,90,89,77,87,86,85,84,83,82,81,80,79,78,66,76,75,74,73,72,71,70,69,68,67 %N A055121 Base-11 complement of n (write n in base 11, then replace each digit with its base-11 negative). %H A055121 Alois P. Heinz, <a href="/A055121/b055121.txt">Table of n, a(n) for n = 0..1330</a> %H A055121 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %Y A055121 Cf. A004488, A048647, A055115-A055126. %Y A055121 Column k=11 of A248813. %K A055121 base,easy,nonn %O A055121 0,2 %A A055121 _Henry Bottomley_, Apr 19 2000