|
| |
|
|
A047728
|
|
Intersection of A046985 and A007691: multiply perfect, refactorable numbers with integer average divisor dividing the number.
|
|
0
| |
|
|
1, 672, 30240, 23569920, 45532800, 14182439040, 153003540480, 403031236608, 13661860101120, 154345556085770649600, 143573364313605309726720, 352338107624535891640320, 680489641226538823680000
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,2
|
|
|
COMMENTS
| Colton proves (link in A033950) that perfect numbers (A000396) cannot be refactorable.
|
|
|
FORMULA
| All of these four quotients are integers: s1/s0, (x*s0)/s1, s1/x, x/s0.
|
|
|
EXAMPLE
| x=45532800, s0=Sigma[ 0,x ]=384, s1=Sigma[ 1,x ]=571963392; Four quotients are all integral: a=s1/s0=474300, b=x/a=96, c=s1/x=4 and q=x/s0=118580.
|
|
|
CROSSREFS
| Cf. A000396, A046985, A001599, A007691.
Sequence in context: A057796 A057797 A057802 * A160209 A171266 A158392
Adjacent sequences: A047725 A047726 A047727 * A047729 A047730 A047731
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Labos E. (labos(AT)ana.sote.hu)
|
|
|
EXTENSIONS
| a(7)-a(13) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Apr 09 2010
|
| |
|
|
