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 A353827 #8 May 10 2022 02:26:23
%S A353827 0,1,2,3,4,8,6,7,5,9,10,20,12,13,17,24,25,23,18,19,11,21,22,26,15,16,
%T A353827 14,27,28,56,30,31,35,60,61,59,36,37,47,39,40,44,51,52,50,72,73,65,75,
%U A353827 76,80,69,70,68,54,55,29,57,58,62,33,34,32,63,64,74,66,67
%N A353827 Inverse permutation to A353826.
%H A353827 Rémy Sigrist, <a href="/A353827/b353827.txt">Table of n, a(n) for n = 0..6561</a>
%H A353827 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%e A353827 A353826(11) = 20, so a(20) = 11.
%o A353827 (PARI) a(n) = { my (d=digits(n,3), p=Mod(1,3)); forstep (k=#d, 1, -1, if (d[k], p*=d[k]=lift(d[k]/p))); fromdigits(d, 3) }
%Y A353827 Cf. A353826.
%K A353827 nonn,base
%O A353827 0,3
%A A353827 _Rémy Sigrist_, May 08 2022