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 A324078 #18 Feb 16 2024 01:31:39
%S A324078 1,1,1,1,3,3,1,3,2,2,1,2,2,3,3,2,4,4,1,4,2,4,3,4,4,2,6,6,1,6,2,6,3,6,
%T A324078 4,6,5,5,1,5,2,5,3,5,4,5,5,6,6,5,7,7,1,7,2,7,3,7,4,7,5,7,6,7,7,3,9,9,
%U A324078 1,9,2,9,3,9,4,9,5,9,6,9,7,9,8,8,1,8,2,8,3,8,4,8,5,8,6,8,7,8,8,9,9,8,10,10,1,10,2,10,3,10
%N A324078 a(0) = 1, followed by pairs (value of rarest term, multiplicity of that value). Choose the least value of rarest term if there is a tie.
%H A324078 Joerg Arndt, <a href="/A324078/b324078.txt">Table of n, a(n) for n = 0..10000</a>
%e A324078 1, term 1 appears 1 time, term 1 appears 3 times, term 3 appears 1 time, term 3 appears 2 times, term 2 appears 1 time, ...
%t A324078 Nest[Append[#, First@ SortBy[Union@ Tally[Flatten@ #], Last]] &, {{1}}, 55] // Flatten (* _Michael De Vlieger_, Feb 25 2019 *)
%Y A324078 A324079 is the same sequence with pairs after a(0) swapped.
%Y A324078 A324080 is the sequence of rarest values, A324081 gives their multiplicities.
%K A324078 nonn
%O A324078 0,5
%A A324078 _Joerg Arndt_, Feb 15 2019