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 A364290 #8 Jul 25 2023 12:31:12
%S A364290 1,2,4,8,9,15,16,18,25,27,30,32,35,36,45,49,50,54,60,63,64,70,72,75,
%T A364290 77,81,90,98,100,105,108,120,121,125,126,128,135,140,143,144,147,150,
%U A364290 154,162,165,169,175,180,189,196,200,210,216,225,231,240,242,243,245,250,252,256,270,273,275,280,286,288,289,294
%N A364290 Numbers k such that A243071(k) < k.
%C A364290 If k is present, then 2*k is also present, and vice versa.
%C A364290 361 = 19^2 is the first square that is not present in this sequence.
%o A364290 (PARI)
%o A364290 A064989(n) = { my(f=factor(n>>valuation(n,2))); for(i=1, #f~, f[i,1] = precprime(f[i,1]-1)); factorback(f); };
%o A364290 A243071(n) = if(n<=2, n-1, if(!(n%2), 2*A243071(n/2), 1+(2*A243071(A064989(n)))));
%o A364290 isA364290(n) = (A243071(n)<n);
%Y A364290 Positions of strictly positive terms in A364288.
%Y A364290 Subsequence of A364291.
%Y A364290 Cf. A243071, A364289 (complement).
%Y A364290 Cf. also A364287.
%K A364290 nonn
%O A364290 1,2
%A A364290 _Antti Karttunen_, Jul 25 2023