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 A368825 #10 Jan 07 2024 09:45:40 %S A368825 1,3,6,10,15,21,7,15,3,13,3,15,7,21,1,17,34,13,1,21,42,1,3,1,26,13,5, %T A368825 33,62,23,2,34,67,101,17,53,10,3,42,82,123,165,13,57,102,37,21,69,118, %U A368825 21,1,53,106,5,15,71,1,59,118,178,239,301,91,155,55,1,17,85,154,7,78,6,79,17,23,11 %N A368825 a(1) = 1; for n > 1, a(n) = A055231(a(n-1) + n), where A055231(k) is the powerfree part of k. %C A368825 The sequence is conjectured to contain all the squarefree numbers; see A005117. %C A368825 The fixed points begin 1, 7, 5759, 35435, 58403, 62051, 182363, 261763, ... , although it is likely there are infinitely more. %C A368825 See A368827 for the indices where a(n) = 1. %H A368825 Scott R. Shannon, <a href="/A368825/b368825.txt">Table of n, a(n) for n = 1..10000</a> %H A368825 Scott R. Shannon, <a href="/A368825/a368825.png">Image of the first 1000000 terms</a>. The green line is a(n) = n. %e A368825 a(9) = 3 as a(8)+9 = 15+9 = 24 = 2*2*2*3, and the powerfree part of 24 is 3. %Y A368825 Cf. A368827, A368823 (multiplication), A055231, A005117, A124010. %K A368825 nonn %O A368825 1,2 %A A368825 _Scott R. Shannon_, Jan 07 2024