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 A115308 #9 Mar 28 2025 13:21:09 %S A115308 1,2,3,4,5,6,7,15,14,13,12,11,10,9,8,23,22,21,20,19,18,17,16,31,30,29, %T A115308 28,27,26,25,24,39,38,37,36,35,34,33,32,47,46,45,44,43,42,41,40,55,54, %U A115308 53,52,51,50,49,48,63,62,61,60,59,58,57,56,127,126,125,124,123,122,121 %N A115308 a(n) = if n<8 then n else 8*a(floor(n/8)) + 7 - n mod 8. %C A115308 Self-inverse permutation of the natural numbers; %C A115308 A115310(n+6,7) = a(n); %C A115308 if n is written in octal representation, then a(n) is the value after replacing all digits d (but not the leading one) by 7-d. %H A115308 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A115308 a(n) = n XOR (8^floor(log_8(n)) - 1). - _Alan Michael Gómez Calderón_, Mar 27 2025 %Y A115308 Cf. A054429, A115303, A115304, A115305, A115306, A115307, A115309, A106649. %K A115308 nonn,base %O A115308 1,2 %A A115308 _Reinhard Zumkeller_, Jan 20 2006