This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A066242 The floor((Log x)^2)-perfect numbers, where f-perfect numbers for an arithmetical function f are defined in A066218. 0
 2, 18, 20, 32, 45, 63 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS J. Pe, On a Generalization of Perfect Numbers, J. Rec. Math., 31(3) (2002-2003), 168-172. EXAMPLE 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. MATHEMATICA f[x_ ] := Floor[Log[x]^2]; Select[ Range[2, 10^5], 2 * f[ # ] == Apply[ Plus, Map[ f, Divisors[ # ] ] ] & ] CROSSREFS Sequence in context: A076378 A231502 A231864 * A022371 A299380 A266956 Adjacent sequences:  A066239 A066240 A066241 * A066243 A066244 A066245 KEYWORD nonn AUTHOR Joseph L. Pe, Dec 19 2001 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 23 17:13 EST 2019. Contains 319399 sequences. (Running on oeis4.)