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 A386423 #11 Jul 22 2025 13:10:18
%S A386423 1,3,5,9,13,15,35,63,77,81,99,105,135,175,189,455,765,775,819,945,
%T A386423 2125,6375,9261,21275,43011,43125,43475,44469,45441,45617,45619,46189,
%U A386423 46305,155363,161257,203203,318835,401625,1016015,1128799,1773827,3048045,3255075,3386397,4044555
%N A386423 Odd numbers k such that k/(1+A347381(k)) obtains record values, where A347381 gives the distance from n to the nearest common ancestor of n and sigma(n) in the Doudna-tree.
%C A386423 Odd terms of A347391 probably form a subsequence, especially if there are no odd perfect numbers or other odd terms larger than one in A336702.
%H A386423 <a href="/index/O#opnseqs">Index entries for sequences where odd perfect numbers must occur, if they exist at all</a>
%o A386423 (PARI) m=-1; n=-1; k=0; while(m!=0, n+=2; if(!((n-1)%(2^25)),print1("("n")")); my(r=n/(1+A347381(n))); if(r>m, m=r; k++; write("b386423.txt", k, " ", n); print1(n, ", ")));
%Y A386423 Cf. A000203, A005940, A336702, A347381, A347391.
%Y A386423 Cf. also A119239, A171929, A228059.
%K A386423 nonn,more
%O A386423 1,2
%A A386423 _Antti Karttunen_, Jul 21 2025