A221368 - OEIS

A221368

A two-digit Look-and-Say sequence starting with 12: each term summarizes the increasing two-digit substrings of the previous term.

12, 112, 111112, 411112, 311112141, 311112114121131141, 611212113214221231241, 211412113114421122123124131132141142161, 611412313414116621122123124331132341242144161, 411512213314216321122323224331132133234541142143144261162166

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OFFSET

0,1

COMMENTS

a(36) is the first term containing a zero; this is due to the fact that a(35) is the first term having exactly 10 occurrences of a two-digit number, namely 10 x 42.

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) = 12: 1 x 12 --> a(1) = 112;

a(1) = 112: 1 x 11 ana 1 x 12 --> a(2) = 111112;

a(2) = 111112: 4 x 11 and 1 x 12 --> a(4) = 411112;

a(3) = 411112: 3 x 11, 1 x 12 and 1 x 41 --> a(4) = 311112141.

PROG

(Haskell) -- See Link.