A244112 Reverse digit count of n in decimal representation.

10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 1110, 21, 1211, 1311, 1411, 1511, 1611, 1711, 1811, 1911, 1210, 1211, 22, 1312, 1412, 1512, 1612, 1712, 1812, 1912, 1310, 1311, 1312, 23, 1413, 1513, 1613, 1713, 1813, 1913, 1410, 1411, 1412, 1413, 24, 1514, 1614, 1714

Offset: 0

Author

Reinhard Zumkeller, Nov 11 2014

Keywords

• nonn
• base

Comments

Frequencies of digits 0 through 9, occurring in n, are summarized in order of decreasing digits;

a(A010785(n)) = A047842(A010785(n)).

Examples

			101 contains two 1s and one 0, therefore a(101) = 2110;
102 contains one 2, one 1 and one 0, therefore a(102) = 121110.
		

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A047842, A010785.

See A036058 for the orbit of 0 under this map.

Programs

Haskell

import Data.List (sort, group); import Data.Function (on)
a244112 :: Integer -> Integer
a244112 n = read $ concat $
   zipWith ((++) `on` show) (map length xs) (map head xs)
   where xs = group $ reverse $ sort $ map (read . return) $ show n

Mathematica

f[n_] := Block[{s = Split@ IntegerDigits@ n}, FromDigits@ Reverse@ Riffle[Union@ Flatten@ s, Length@# & /@ s]]; Array[f, 48, 0] (* Robert G. Wilson v, Dec 01 2016 *)

PARI

A244112(n,c=1,S="")={for(i=2,#n=vecsort(digits(n),,4),n[i]==n[i-1]&&c++&&next;S=Str(S,c,n[i-1]);c=1);eval(Str(S,c,if(n,n[#n])))} \\ M. F. Hasler, Feb 25 2018

Python

def A244112(n):
    return int(''.join([str(str(n).count(d))+d for d in '9876543210' if str(n).count(d) > 0])) # Chai Wah Wu, Dec 01 2016