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 A115306 #13 Aug 17 2024 23:14:12
%S A115306 1,2,3,4,5,11,10,9,8,7,6,17,16,15,14,13,12,23,22,21,20,19,18,29,28,27,
%T A115306 26,25,24,35,34,33,32,31,30,71,70,69,68,67,66,65,64,63,62,61,60,59,58,
%U A115306 57,56,55,54,53,52,51,50,49,48,47,46,45,44,43,42,41,40,39,38,37,36,107
%N A115306 a(n) = if n<6 then n else 6*a(floor(n/6)) + 5 - n mod 6.
%C A115306 Self-inverse permutation of the natural numbers;
%C A115306 if n is written in base 6 representation, then a(n) is the value after replacing all digits d (but not the leading one) by 5-d.
%H A115306 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%F A115306 a(n) = A115310(n+4, 5).
%t A115306 a[n_]:=If[n<6,n,6*a[Floor[n/6]]+5-Mod[n,6]];Table[a[n],{n,72}] (* _James C. McMahon_, Aug 11 2024 *)
%Y A115306 Cf. A054429, A115303, A115304, A115305, A115307, A115308, A115309, A106649.
%K A115306 nonn,base,easy
%O A115306 1,2
%A A115306 _Reinhard Zumkeller_, Jan 20 2006