A087246 Squarefree deficient numbers.

1, 2, 3, 5, 7, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 26, 29, 31, 33, 34, 35, 37, 38, 39, 41, 43, 46, 47, 51, 53, 55, 57, 58, 59, 61, 62, 65, 67, 69, 71, 73, 74, 77, 79, 82, 83, 85, 86, 87, 89, 91, 93, 94, 95, 97, 101, 103, 105, 106, 107, 109, 110, 111, 113, 115, 118, 119

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

All primes are here.
Numerous composite solutions:See A087247.
n=21=3.7 and sigma[21]=1+3+7+21=32<2.21=42.

Mathematica

Select[Range[120], SquareFreeQ[#] && DivisorSigma[1, #] < 2 # &] (* Amiram Eldar, Aug 03 2019 *)

Crossrefs

Cf. A000203, A005100, A005117, A013929, A087244-A087247, A008683.

Sequence in context: A121232 A298746 A122428 * A090421 A109608 A325388

Adjacent sequences: A087243 A087244 A087245 * A087247 A087248 A087249

Keyword

nonn

Author

Labos Elemer, Sep 09 2003

Status

approved