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

Author

Labos Elemer, Sep 09 2003

Keywords

• nonn

Examples

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

Links

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

Crossrefs

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

Programs

Mathematica

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