|
| |
|
|
A050480
|
|
Numbers that can be written as a concatenation of distinct proper divisors.
|
|
1
| |
|
|
12, 15, 24, 36, 48, 110, 120, 124, 125, 126, 128, 132, 135, 150, 162, 168, 175, 184, 210, 216, 220, 240, 248, 250, 264, 312, 315, 324, 330, 360, 375, 384, 396, 412, 416, 420, 432, 440, 480, 510, 520, 525, 550, 612, 624, 630, 648, 660, 672, 714, 728, 735
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| The number of terms less than 10^k: 0, 5, 64, 395, 2406, 13417, 78268, ..., . Robert G. Wilson v, Apr 4 2011.
|
|
|
LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..1000
|
|
|
EXAMPLE
| 132 is divisible by 1, 3 & 2.
|
|
|
MATHEMATICA
| f[x_, y_] := (y == Take[x, Min[Length@ y, Length@ x]]); g[{}, _] := True; g[LL_, DD_] := Module[{a = Select[DD, f[LL, IntegerDigits@ #] &]}, Or @@ Map[ g[ Drop[ LL, Length@ IntegerDigits@ #], Complement[DD, {#}]] &, a]]; fQ[n_] := g[IntegerDigits@ n, Most@ Divisors@ n]; Select[ Range@ 2000, fQ] (* Robert G. Wilson v, Apr 4 2011 *)
|
|
|
PROG
| (Haskell)
import Data.List (permutations, subsequences, isInfixOf)
a050480 n = a050480_list !! (n-1)
a050480_list = filter chi [2..] where
chi x = xs `elem` (map concat $ choices divs) where
choices = concat . (map permutations) . subsequences
divs = filter (`isInfixOf` xs)
$ map show $ filter ((== 0) . mod x) [1..a032742 x]
xs = show x
-- Reinhard Zumkeller, Apr 04 2011
|
|
|
CROSSREFS
| Cf. A032742.
Sequence in context: A162820 A158190 A122040 * A063604 A015904 A124521
Adjacent sequences: A050477 A050478 A050479 * A050481 A050482 A050483
|
|
|
KEYWORD
| base,easy,nice,nonn
|
|
|
AUTHOR
| Erich Friedman (efriedma(AT)stetson.edu), Dec 24 1999
|
|
|
EXTENSIONS
| Offset adjusted by Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 04 2011
|
| |
|
|
