

A054010


Numbers n with property that n is divisible by the number of its proper divisors.


4



2, 3, 4, 5, 6, 7, 11, 13, 15, 16, 17, 19, 20, 21, 23, 27, 29, 31, 33, 37, 39, 41, 42, 43, 45, 47, 50, 51, 53, 56, 57, 59, 61, 67, 69, 70, 71, 73, 75, 79, 83, 87, 89, 93, 97, 101, 103, 105, 107, 109, 111, 113, 120, 123, 127, 129, 131, 132, 137, 139, 141, 149, 151, 154
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OFFSET

1,1


COMMENTS

All primes are in this sequence, having only one proper divisor. The specifically nonprime members of this sequence are in A055719.  Carl R. White, Jul 11 2012


LINKS

Carl R. White, Table of n, a(n) for n = 1..10000


FORMULA

Numbers n such that A054009(n) = 0.


EXAMPLE

There are three proper divisors of 6, {1, 2, 3}, 6 is divisible by 3.


MAPLE

[seq(`if`(i mod (tau(i)1) = 0, i, print( )), i=2..190)];


MATHEMATICA

Select[Range[2, 100], IntegerQ[ #/(1+DivisorSigma[0, # ])]&] (* Wouter Meeussen, Jun 07 2005 *)


CROSSREFS

Cf. A032741, A033950, A054009, A055719.
Sequence in context: A280536 A090563 A045745 * A051948 A193461 A192587
Adjacent sequences: A054007 A054008 A054009 * A054011 A054012 A054013


KEYWORD

nonn


AUTHOR

Asher Auel (asher.auel(AT)reed.edu), Jan 12 2000


STATUS

approved



