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 A380507 #9 Jan 31 2025 01:42:01 %S A380507 1,2,1,3,1,3,4,3,5,3,4,6,7,8,4,6,9,7,4,6,10,11,4,6,10,12,4,6,10,13,4, %T A380507 6,10,14,4,6,10,13,15,6,10,16,14,6,10,13,17,6,10,18,19,6,10,13,20,6, %U A380507 10,18,21,6,10,13,22,6,10,18,23,6,10,13,24,6,10,18,22 %N A380507 Lexicographically earliest infinite sequence of positive integers such that for any n, consecutive occurrences of n are separated by a(n) terms and each subsequence enclosed by consecutive equal values is distinct. %C A380507 Endpoints are included when comparing subsequences enclosed by consecutive equal values. %H A380507 Neal Gersh Tolunsky, <a href="/A380507/b380507.txt">Table of n, a(n) for n = 1..10000</a> %e A380507 a(1) = 1 means that consecutive 1s enclose 1 term. For example: a(1..3) = [1,2,1] encloses [2]. %e A380507 a(2) = 2 means that consecutive 2s have length 2. In this case, there are no subsequences enclosed by a pair of 2s. %e A380507 a(3) = 1 means that consecutive 3s enclose 1 term. For example, a(3..5) = [3,1,3] encloses [1]. %e A380507 a(7) = 4: a(7) cannot be 1 as this would repeat the subsequence [1,3,1], which was seen before at a(3..5). 2 and 3 would not enclose a(2) = 2 and a(3) = 1 terms respectively. So a(7) = 4, which has not occurred thus far. %Y A380507 Cf. A363654, A380278, A380495. %K A380507 nonn %O A380507 1,2 %A A380507 _Neal Gersh Tolunsky_, Jan 25 2025