A055719 d(n)-1 | n and n is not prime.

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

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 * A349157 A117883 A106387

Adjacent sequences: A055716 A055717 A055718 * A055720 A055721 A055722

Keyword

nonn

Author

Robert G. Wilson v, Jun 09 2000

Status

approved