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 A383339 #14 May 03 2025 14:23:11 %S A383339 1,1,1,2,1,1,3,2,1,1,4,2,2,5,3,1,1,6,3,3,7,4,1,2,2,8,4,1,2,4,2,2,9,5, %T A383339 1,1,10,5,5,11,6,1,3,2,1,3,4,1,5,1,3,3,12,6,1,4,1,4,5,2,1,6,2,6,6,13, %U A383339 7,1,2,4,2,7,5,1,5,8,1,7,6,2,2,14,6,7,7,15 %N A383339 a(1)=1; thereafter if a(n-1) is a first occurrence, then a(n) is the number of first occurrences in the sequence thus far. Otherwise; a(n) is the number of terms that are the same distance away from their previous last occurrence as a(n-1). %C A383339 Alternatively, a(n) is the number of terms with the same Backwards van Eck transform as a(n-1). %H A383339 Neal Gersh Tolunsky, <a href="/A383339/b383339.txt">Table of n, a(n) for n = 1..10000</a> %H A383339 Neal Gersh Tolunsky, <a href="/A383339/a383339.png">Backwards van Eck transform of the first 400000 terms</a> %H A383339 Neal Gersh Tolunsky, <a href="/A383339/a383339_1.png">Graph of the first 400000 terms</a> %e A383339 a(14) = 5: a(13) = 2 has a distance of 1 from its previous last occurrence a(12) = 2. There are 5 terms in total with a distance of 1 from their previous last occurrence; they are at indices i = 2,3,6,10,13. So a(14) = 5. %Y A383339 Cf. A383340, A383421. %K A383339 nonn %O A383339 1,4 %A A383339 _Neal Gersh Tolunsky_, Apr 23 2025