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 A364561 #18 Aug 11 2023 09:59:14
%S A364561 1,3,5,9,15,21,25,27,35,45,49,55,63,75,77,81,91,99,105,121,125,135,
%T A364561 143,147,165,169,175,187,189,195,221,225,231,243,245,273,275,289,297,
%U A364561 315,323,325,343,351,357,363,375,385,405,425,429,441,455,495,507,525,539,561,567,585,595,605,625,627,637,663,665
%N A364561 Odd numbers k for which A156552(k) < k.
%C A364561 Odd numbers k such that A005941(k) <= k.
%H A364561 Antti Karttunen, <a href="/A364561/b364561.txt">Table of n, a(n) for n = 1..13739; terms less than 2^21</a>
%o A364561 (PARI)
%o A364561 A156552(n) = { my(f = factor(n), p, p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res };
%o A364561 isA364561(n) = ((n%2)&&(A156552(n) < n));
%Y A364561 Odd terms in A364560.
%Y A364561 Cf. A005940, A005941, A156552, A364545, A364564 (largest prime factor).
%Y A364561 Cf. also A364551, A364576 (subsequences).
%K A364561 nonn
%O A364561 1,2
%A A364561 _Antti Karttunen_, Jul 28 2023