A022520 Describe previous term from the right (method B - initial term is 9).

9, 91, 1191, 119112, 21129112, 211291211221, 112212211191211221, 1122122111911322112212, 21112212223112911322112212, 21112212223112912112312311221321

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• base
• easy
• nice

Comments

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

Examples

			The term after 1191 is obtained by saying "1 once, 9 once, 1 twice", which gives 119112.
		

Links

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

Crossrefs

Cf. A022481, A022488, A022514-A022519.

Programs

Haskell

import Data.List (group, transpose)
a022520 n = a022520_list !! n
a022520_list = 9 : f [9] :: [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

Extensions

More terms from Patrick De Geest, Jun 15 1999