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 A342217 #18 Mar 07 2021 14:41:18 %S A342217 0,3,2,1,14,15,12,13,8,11,10,9,6,7,4,5,58,57,56,59,60,63,62,61,50,49, %T A342217 48,51,52,55,54,53,32,35,34,33,46,47,44,45,40,43,42,41,38,39,36,37,26, %U A342217 25,24,27,28,31,30,29,18,17,16,19,20,23,22,21,234,235,232 %N A342217 The n-th and a(n)-th points of the Hilbert's Hamiltonian walk (A059252, A059253) are symmetrical with respect to the line X=Y. %C A342217 In other words, a(n) is the unique k such that A059252(n) = A059253(k) and A059253(n) = A059252(k). %C A342217 This sequence is a self-inverse permutation of the nonnegative integers. %H A342217 Rémy Sigrist, <a href="/A342217/b342217.txt">Table of n, a(n) for n = 0..4095</a> %H A342217 Rémy Sigrist, <a href="/A342217/a342217.gp.txt">PARI program for A342217</a> %H A342217 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the nonnegative integers</a> %F A342217 a(n) = n iff n belongs to A062880. %F A342217 a(n) < 16^k for any n < 16^k. %e A342217 The Hilbert's Hamiltonian walk (A059252, A059253) begins as follows: %e A342217 + +-----+-----+ %e A342217 |15 |12 11 |10 %e A342217 | | | %e A342217 +-----+ +-----+ %e A342217 14 13 |8 9 %e A342217 | %e A342217 +-----+ +-----+ %e A342217 |1 |2 7 |6 %e A342217 | | | %e A342217 + +-----+-----+ %e A342217 0 3 4 5 %e A342217 - so a(0) = 0, %e A342217 a(1) = 3, %e A342217 a(2) = 2, %e A342217 a(4) = 14, %e A342217 a(5) = 15, %e A342217 a(7) = 13, %e A342217 a(8) = 8, %e A342217 a(9) = 11, %e A342217 a(10) = 10. %o A342217 (PARI) See Links section. %Y A342217 See A342218 and A342224 for similar sequences. %Y A342217 Cf. A059252, A059253, A062880. %K A342217 nonn %O A342217 0,2 %A A342217 _Rémy Sigrist_, Mar 05 2021