A022519 Describe previous term from the right (method B - initial term is 8).

8, 81, 1181, 118112, 21128112, 211281211221, 112212211181211221, 1122122111811322112212, 21112212223112811322112212, 21112212223112812112312311221321

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• base
• easy
• nice

Comments

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

Examples

			The term after 1181 is obtained by saying "1 once, 8 once, 1 twice", which gives 118112.
		

Links

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

Crossrefs

Cf. A022481, A022488, A022514-A022520.

Programs

Haskell

import Data.List (group, transpose)
a022519 n = a022519_list !! n
a022519_list = 8 : f [8] :: [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

Python

from itertools import groupby
A022519_list = [8]
for _ in range(10):
    A022519_list.append(int(''.join(str(k)+str(len(list(g))) for k, g in groupby(str(A022519_list[-1])[::-1])))) # Chai Wah Wu, Sep 01 2021

Extensions

More terms from Patrick De Geest, Jun 15 1999