A221373 - OEIS

A221373

A two-digit Look-and-Say sequence starting with 99: each term summarizes the increasing two-digit substrings of the previous term.

99, 199, 119199, 111219191199, 311112319121291199, 411312219121123129231291199, 311512113219221122223229331141291192199, 511312113114115319421522123229231232133141151191292193199, 611412313214315419521222323229631232133241142251152153191292193194199

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,1

COMMENTS

a(22) is the first term containing a zero; this is due to the fact that a(21) is the first term having exactly 10 occurrences of a two-digit number, namely 10 x 32.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..1000

Eric Weisstein's World of Mathematics, Look and Say Sequence

Wikipedia, Look-and-say sequence

Reinhard Zumkeller, Haskell program for two-digit Look-and-Say sequences

EXAMPLE

a(0) = 11: 1x99 --> a(1)=199;

a(1) = 199: 1x19 and 1x99 --> a(2)=119199;

a(2) = 119199: 1x11, 2x19, 1x91 and 1x99 --> a(3)=111219191199;

a(3) = 111219191199: 3x11, 1x12, 3x19, 1x21, 2x91 and 1x99 --> a(4)=311112319121291199.

PROG

(Haskell) -- See Link.