A022515 Describe previous term from the right (method B - initial term is 4).

4, 41, 1141, 114112, 21124112, 211241211221, 112212211141211221, 1122122111411322112212, 21112212223112411322112212, 21112212223112412112312311221321

Offset

0,1

Comments

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

Links

Reinhard Zumkeller, Table of n, a(n) for n = 0..21

Example

The term after 1141 is obtained by saying "1 once, 4 once, 1 twice", which gives 114112.

Mathematica

A022515[1]:=4; A022515[n_]:=A022515[n]=FromDigits[Flatten[{First[#], Length[#]}&/@Split[Reverse[IntegerDigits[A022515[n-1]]]]]]; Map[A022515, Range[15]] (* Peter J. C. Moses, Apr 22 2013 *)

Prog

(Haskell)
import Data.List (group, transpose)
a022515 n = a022515_list !! n
a022515_list = 4 : f [4] :: [Integer] where
   f xs = (read $ concatMap show ys) : f ys where
          ys = concat $ transpose [map head zss, map length zss]
          zss = reverse $ group xs
-- Reinhard Zumkeller, Jan 26 2014

Crossrefs

Cf. A022481, A022488, A022514-A022520.

Sequence in context: A284276 A327026 A244751 * A172496 A059730 A006825

Adjacent sequences: A022512 A022513 A022514 * A022516 A022517 A022518

Keyword

nonn,base,easy,nice

Author

N. J. A. Sloane

Extensions

More terms from Patrick De Geest, Jun 15 1999

Status

approved