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 A347540 #16 Oct 25 2021 03:21:35 %S A347540 1,2,3,4,5,7,6,8,15,12,9,16,11,14,29,17,10,35,13,30,33,22,26,36,71,28, %T A347540 82,34,21,73,18,37,55,25,72,83,27,32,69,74,20,80,24,56,183,66,52,84, %U A347540 79,180,63,70,31,197,144,81,77,54,19,184,65,43,194,85,176,146 %N A347540 Position within Beyer and Hedetniemi's rooted tree iteration (A346913) of the tree with Matula-Goebel number n. %C A347540 This sequence is a permutation of the natural numbers, with inverse A347539. %H A347540 Kevin Ryde, <a href="/A347540/b347540.txt">Table of n, a(n) for n = 1..7813</a> %H A347540 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %e A347540 For n=21, the tree with Matula-Goebel number 21 is as follows, shown with siblings ordered per Beyer and Hedetniemi's canonical form, %e A347540 root 1 pre-order levels = 1,2,3,3,2,3 %e A347540 | \ which is row 33 of A346913 %e A347540 level=2 2 2 so a(21) = 33 %e A347540 |\ | %e A347540 level=3 3 3 3 %Y A347540 Cf. A346913, A347539 (inverse). %K A347540 nonn %O A347540 1,2 %A A347540 _Kevin Ryde_, Sep 06 2021