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A055719 d(n)-1 | n and n is not prime. 3
4, 6, 15, 16, 20, 21, 27, 33, 39, 42, 45, 50, 51, 56, 57, 69, 70, 75, 87, 93, 105, 111, 120, 123, 129, 132, 141, 154, 159, 162, 175, 177, 182, 183, 189, 198, 201, 210, 213, 219, 220, 231, 237, 238, 245, 249, 256, 266, 267, 270, 273, 275, 291, 303, 308, 309, 321 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Composite integers divisible by 1 less than the number of their divisors.

This is, composite members of A054010. - Carl R. White, Jul 11 2012

LINKS

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

MATHEMATICA

Do[ If[ !PrimeQ[ n ], If[ IntegerQ[ n/(DivisorSigma[ 0, n ]-1) ], Print[ n ] ] ], {n, 1, 500} ]

Select[Range[2, 400], !PrimeQ[#]&&Divisible[#, DivisorSigma[0, #]-1]&] (* Harvey P. Dale, Mar 13 2013 *)

CROSSREFS

Cf. A054010.

Sequence in context: A135093 A141667 A048753 * A117883 A106387 A034771

Adjacent sequences:  A055716 A055717 A055718 * A055720 A055721 A055722

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Jun 09 2000

STATUS

approved

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Last modified August 23 22:45 EDT 2019. Contains 326254 sequences. (Running on oeis4.)