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 A338249 #18 Oct 19 2020 12:30:00 %S A338249 0,2,1,8,7,10,9,4,3,6,5,32,31,34,33,28,27,30,29,40,39,42,41,36,35,38, %T A338249 37,16,15,18,17,12,11,14,13,24,23,26,25,20,19,22,21,128,127,130,129, %U A338249 124,123,126,125,136,135,138,137,132,131,134,133,112,111,114,113 %N A338249 Nonpositive values in A053985, in order of appearance and negated. %C A338249 This sequence is a self-inverse permutation of the nonnegative integers (the offset has been set to 0 so as to get a permutation). %C A338249 There is only one fixed point: a(0) = 0. %H A338249 Rémy Sigrist, <a href="/A338249/b338249.txt">Table of n, a(n) for n = 0..10922</a> %H A338249 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A338249 a(n) = -A053985(A053754(n+1)) for any n >= 0. %e A338249 A053985 = 0, 1, -2, -1, 4, 5, 2, 3, -8, -7, -10, -9, -4, -3, -6, -5, ... %e A338249 We keep: 0, 2, 1, 8, 7, 10, 9, 4, 3, 6, 5, ... %o A338249 (PARI) A053985(n) = fromdigits(binary(n), -2) %o A338249 print (-select(v -> v<=0, apply(A053985, [0..147]))) %Y A338249 Cf. A053754, A053985, A338248. %K A338249 nonn,base %O A338249 0,2 %A A338249 _Rémy Sigrist_, Oct 18 2020