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

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.

Crossrefs

Cf. A005151, A047842.

Cf. A209234 (start=10), A209233 (start=11), A221368 (start=12), A221369 (start=13), A221372 (start=19).

Sequence in context: A031500 A044431 A044812 * A260242 A250734 A260279

Adjacent sequences: A221370 A221371 A221372 * A221374 A221375 A221376

Keyword

nonn,base

Author

Reinhard Zumkeller, Jan 13 2013

Status

approved