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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; text; 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 04 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 04 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: A122040 A274550 A253235 * A290508 A063604 A124521

Adjacent sequences:  A050477 A050478 A050479 * A050481 A050482 A050483

KEYWORD

base,easy,nice,nonn

AUTHOR

Erich Friedman, Dec 24 1999

EXTENSIONS

Offset adjusted by Reinhard Zumkeller, Apr 04 2011

STATUS

approved

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Last modified November 14 09:49 EST 2018. Contains 317182 sequences. (Running on oeis4.)