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A244112 Reverse digit count of n in decimal representation.

%I A244112 #22 Feb 25 2018 02:01:39
%S A244112 10,11,12,13,14,15,16,17,18,19,1110,21,1211,1311,1411,1511,1611,1711,
%T A244112 1811,1911,1210,1211,22,1312,1412,1512,1612,1712,1812,1912,1310,1311,
%U A244112 1312,23,1413,1513,1613,1713,1813,1913,1410,1411,1412,1413,24,1514,1614,1714
%N A244112 Reverse digit count of n in decimal representation.
%C A244112 Frequencies of digits 0 through 9, occurring in n, are summarized in order of decreasing digits;
%C A244112 a(A010785(n)) = A047842(A010785(n)).
%H A244112 Reinhard Zumkeller, <a href="/A244112/b244112.txt">Table of n, a(n) for n = 0..10000</a>
%e A244112 101 contains two 1s and one 0, therefore a(101) = 2110;
%e A244112 102 contains one 2, one 1 and one 0, therefore a(102) = 121110.
%t A244112 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 *)
%o A244112 (Haskell)
%o A244112 import Data.List (sort, group); import Data.Function (on)
%o A244112 a244112 :: Integer -> Integer
%o A244112 a244112 n = read $ concat $
%o A244112    zipWith ((++) `on` show) (map length xs) (map head xs)
%o A244112    where xs = group $ reverse $ sort $ map (read . return) $ show n
%o A244112 (Python)
%o A244112 def A244112(n):
%o A244112     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
%o A244112 (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
%Y A244112 Cf. A047842, A010785.
%Y A244112 See A036058 for the orbit of 0 under this map.
%K A244112 nonn,base
%O A244112 0,1
%A A244112 _Reinhard Zumkeller_, Nov 11 2014