A287661 Smallest odd number with exactly n nonprime divisors.

1, 9, 27, 45, 105, 135, 225, 405, 315, 675, 177147, 1155, 945, 3375, 1575, 6075, 2835, 10125, 18225, 3465, 4725, 30375, 50625, 11025, 25515, 91125, 14175, 10395, 23625, 273375, 1476225, 17325, 33075, 759375, 50031545098999707, 31185, 70875, 1366875, 127575

Offset: 1

Author

Ilya Gutkovskiy, May 29 2017

Keywords

• nonn

Examples

			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.
		

Links

• Giovanni Resta, Table of n, a(n) for n = 1..1000
• Eric Weisstein's World of Mathematics, Divisor

Crossrefs

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

Formula

A033273(a(n)) = n.

Extensions

a(35)-a(39) from Giovanni Resta, May 31 2017