A066242 The floor((log(x))^2)-perfect numbers, where f-perfect numbers for an arithmetical function f are defined in A066218.

2, 18, 20, 32, 45, 63

Offset: 1

Author

Joseph L. Pe, Dec 19 2001

Keywords

• nonn
• more

Examples

			Let f(n) = floor((log(x))^2). Then f(18) = 8 = 4+3+1+0+0 = f(9)+f(6)+f(3)f(2)+f(1); so 18 is a term of the sequence.
		

Links

• J. Pe, On a Generalization of Perfect Numbers, J. Rec. Math., 31(3) (2002-2003), 168-172.

Programs

Mathematica

f[x_ ] := Floor[Log[x]^2]; Select[ Range[2, 10^5], 2 * f[ # ] == Apply[ Plus, Map[ f, Divisors[ # ] ] ] & ]