login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A066238 The floor(n/3)-perfect numbers, where f-perfect numbers for an arithmetical function f are defined in A066218. 0
2, 12, 18, 40, 56, 304, 550, 748, 1504, 3230, 3770, 6976, 29824 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

It appears that there are more floor(n/N)-perfect numbers the larger N is. (Here N = 3.)

LINKS

Table of n, a(n) for n=1..13.

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

EXAMPLE

Let f(n) = floor(n/3). Then f(12) = 6 = 3+2+1+0 = f(6)+f(4)+f(3)+f(1); so 12 is a term of the sequence.

MATHEMATICA

f[x_] := Floor[x/3]; Select[ Range[2, 10^5], 2 * f[ # ] == Apply[ Plus, Map[ f, Divisors[ # ] ] ] & ]

CROSSREFS

Sequence in context: A281353 A257256 A190044 * A101074 A115109 A048001

Adjacent sequences:  A066235 A066236 A066237 * A066239 A066240 A066241

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 18 13:10 EDT 2018. Contains 316321 sequences. (Running on oeis4.)