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 A358503 #35 Nov 22 2022 22:18:09 %S A358503 0,0,0,1,1,2,3,2,3,4,5,6,4,5,7,6,8,9,10,11,7,8,9,12,10,13,11,15,14,16, %T A358503 17,18,19,12,13,15,14,20,16,21,17,22,18,24,19,26,23,25,28,27,29,30,31, %U A358503 32,20,21,22,24,26,23,33,25,34,28,36,27,35,29,38,30,40,31,42 %N A358503 Positions inventory sequence: for stage k >= 2 we record where all the numbers from the two previous stages have appeared, starting with a(0) = 0, a(1) = 0. %C A358503 When the sequence is displayed as a triangle, the row corresponding to stage k >= 2 is a permutation of the numbers from Fibonacci(k) - 1 to Fibonacci(k+2) - 2. %e A358503 As an irregular triangle, the sequence begins: %e A358503 0; %e A358503 0; %e A358503 0, 1; %e A358503 1, 2, 3; %e A358503 2, 3, 4, 5, 6; %e A358503 4, 5, 7, 6, 8, 9, 10, 11; %e A358503 7, 8, 9, 12, 10, 13, 11, 15, 14, 16, 17, 18, 19; %e A358503 ... %e A358503 At stage 5 we look at two previous stages 3 and 4 and see the %e A358503 positions of 1's: 4; %e A358503 positions of 2's: 5, 7; %e A358503 positions of 3's: 6, 8; %e A358503 positions of 4's: 9; %e A358503 positions of 5's: 10; %e A358503 positions of 6's: 11; %e A358503 thus stage 5 is 4, 5, 7, 6, 8, 9, 10, 11. %Y A358503 Cf. A000045, A000071, A001911, A356784, A357317, A357443. %K A358503 nonn,tabf %O A358503 0,6 %A A358503 _Ctibor O. Zizka_, Nov 21 2022