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 A287661 #9 Feb 16 2025 08:33:46
%S A287661 1,9,27,45,105,135,225,405,315,675,177147,1155,945,3375,1575,6075,
%T A287661 2835,10125,18225,3465,4725,30375,50625,11025,25515,91125,14175,10395,
%U A287661 23625,273375,1476225,17325,33075,759375,50031545098999707,31185,70875,1366875,127575
%N A287661 Smallest odd number with exactly n nonprime divisors.
%H A287661 Giovanni Resta, <a href="/A287661/b287661.txt">Table of n, a(n) for n = 1..1000</a>
%H A287661 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Divisor.html">Divisor</a>
%F A287661 A033273(a(n)) = n.
%e A287661 a(5) = 105 because 105 has 8 divisors {1, 3, 5, 7, 15, 21, 35, 105} among which 5 are nonprime {1, 15, 21, 35, 105} and 105 is the smallest odd with exactly 5 nonprime divisors.
%Y A287661 Cf. A001221, A002110, A003680, A005179, A033273, A038547, A055079, A070826.
%K A287661 nonn
%O A287661 1,2
%A A287661 _Ilya Gutkovskiy_, May 29 2017
%E A287661 a(35)-a(39) from _Giovanni Resta_, May 31 2017