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 A287661 Smallest odd number with exactly n nonprime divisors. 1

%I

%S 1,9,27,45,105,135,225,405,315,675,177147,1155,945,3375,1575,6075,

%T 2835,10125,18225,3465,4725,30375,50625,11025,25515,91125,14175,10395,

%U 23625,273375,1476225,17325,33075,759375,50031545098999707,31185,70875,1366875,127575

%N Smallest odd number with exactly n nonprime divisors.

%H Giovanni Resta, <a href="/A287661/b287661.txt">Table of n, a(n) for n = 1..1000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Divisor.html">Divisor</a>

%F A033273(a(n)) = n.

%e 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 Cf. A001221, A002110, A003680, A005179, A033273, A038547, A055079, A070826.

%K nonn

%O 1,2

%A _Ilya Gutkovskiy_, May 29 2017

%E a(35)-a(39) from _Giovanni Resta_, May 31 2017

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Last modified April 1 04:15 EDT 2020. Contains 333155 sequences. (Running on oeis4.)