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A287661 Smallest odd number with exactly n nonprime divisors. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Giovanni Resta, Table of n, a(n) for n = 1..1000

Eric Weisstein's World of Mathematics, Divisor

FORMULA

A033273(a(n)) = n.

EXAMPLE

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.

CROSSREFS

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

Sequence in context: A069069 A031088 A020156 * A062231 A133636 A020208

Adjacent sequences:  A287658 A287659 A287660 * A287662 A287663 A287664

KEYWORD

nonn

AUTHOR

Ilya Gutkovskiy, May 29 2017

EXTENSIONS

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

STATUS

approved

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Last modified October 19 14:50 EDT 2019. Contains 328223 sequences. (Running on oeis4.)