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 A115309 #6 Mar 30 2012 18:50:53 %S A115309 1,2,3,4,5,6,7,8,17,16,15,14,13,12,11,10,9,26,25,24,23,22,21,20,19,18, %T A115309 35,34,33,32,31,30,29,28,27,44,43,42,41,40,39,38,37,36,53,52,51,50,49, %U A115309 48,47,46,45,62,61,60,59,58,57,56,55,54,71,70,69,68,67,66,65,64,63,80 %N A115309 a(n) = if n<9 then n else 9*a(floor(n/9)) + 8 - n mod 9. %C A115309 Self-inverse permutation of the natural numbers; %C A115309 A115310(n+7,8) = a(n); %C A115309 if n is written in base 9 representation, then a(n) is the value after replacing all digits d (but not the leading one) by 8-d. %H A115309 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %Y A115309 Cf. A054429, A115303, A115304, A115305, A115306, A115307, A115308, A106649. %K A115309 nonn,base %O A115309 1,2 %A A115309 _Reinhard Zumkeller_, Jan 20 2006