|
| |
|
|
A036456
|
|
If the number of divisor-function is applied 4 times for any of a[ n ], then the result is the fixed point, i.e. 2.
|
|
1
| |
|
|
12, 18, 20, 24, 28, 30, 32, 40, 42, 44, 45, 48, 50, 52, 54, 56, 63, 66, 68, 70, 75, 76, 78, 80, 88, 92, 98, 99, 102, 104, 105, 110, 112, 114, 116, 117, 124, 128, 130, 135, 136, 138, 144, 147, 148, 152, 153, 154, 162, 164, 165, 170, 171, 172, 174, 175, 176, 182
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| Similar to but different from A007624. Terms like 60,72,84,90,96,108,126, etc. are not present here.
|
|
|
FORMULA
| Nest[ d, a[ n ], 4 ] = 2 for all n or d[ d[ d[ d[ a[ n ] ] ] ] ]=2
|
|
|
EXAMPLE
| a[ 3 ]=20 and a[ 17 ]=63; for both a, d[ a ]=6 and d[ d[ a ] ]=4, the 3rd iterates are 3 and the equilibrium value, i.e. 2 appears as 4th iterates.
|
|
|
CROSSREFS
| Cf. A007624, A036450, A046452, A036453, A036455.
Sequence in context: A025491 A091196 A007624 * A102467 A126706 A123711
Adjacent sequences: A036453 A036454 A036455 * A036457 A036458 A036459
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Labos E. (labos(AT)ana.sote.hu)
|
| |
|
|
