A022514 - OEIS

%I #15 Oct 06 2019 16:55:25

%S 3,31,1131,113112,21123112,211231211221,112212211131211221,

%T 1122122111311322112212,21112212223112311322112212,

%U 21112212223112312112312311221321

%N Describe previous term from the right (method B - initial term is 3).

%C Method B = 'digit'-indication followed by 'frequency'.

%H Reinhard Zumkeller, <a href="/A022514/b022514.txt">Table of n, a(n) for n = 0..21</a>

%e The term after 1131 is obtained by saying "1 once, 3 once, 1 twice", which gives 113112.

%t A022514[1]:=3;A022514[n_]:=A022514[n]=FromDigits[Flatten[{First[#],Length[#]}&/@Split[Reverse[IntegerDigits[A022514[n-1]]]]]];Map[A022514,Range[15]] (* _Peter J. C. Moses_, Apr 22 2013 *)

%o (Haskell)

%o import Data.List (group, transpose)

%o a022514 n = a022514_list !! n

%o a022514_list = 3 : f [3] :: [Integer] where

%o    f xs = (read $ concatMap show ys) : f ys where

%o           ys = concat $ transpose [map head zss, map length zss]

%o           zss = reverse $ group xs

%o -- _Reinhard Zumkeller_, Jan 26 2014

%Y Cf. A022481, A022488, A022515-A022520.

%K nonn,base,easy,nice

%O 0,1

%A _N. J. A. Sloane_

%E More terms from _Patrick De Geest_, Jun 15 1999