A166069 Multiply perfect numbers k such that sigma(k)/k > 2.

120, 672, 30240, 32760, 523776, 2178540, 23569920, 45532800, 142990848, 459818240, 1379454720, 1476304896, 14182439040, 31998395520, 43861478400, 51001180160, 66433720320, 153003540480, 403031236608, 518666803200

Offset: 1

Author

Jaroslav Krizek, Oct 06 2009

Keywords

• nonn

Comments

Subsequence of multiply perfect numbers (A007691). Numbers k = A007691(n) such that sigma(A007691(n))/A007691(n) > 2. Numbers k = A007691(n) such that A054030(n) > 2.

Examples

			For n = 1 the a(1) = 120, sigma(120) / 120 = 360 / 120 = 3, i.e. > 2.
		

Links

• Charles R Greathouse IV, Table of n, a(n) for n=1..1587
• Achim Flammenkamp, The Multiply Perfect Numbers Page

Programs

PARI

isok(n) = sn = sigma(n)/n ; (type(sn) == "t_INT") && (sn > 2); \\ Michel Marcus, Oct 24 2013

Extensions

Extended by Charles R Greathouse IV, Oct 12 2009