A221372 - OEIS

A221372

A two-digit Look-and-Say sequence starting with 19: each term summarizes the increasing two-digit substrings of the previous term.

19, 119, 111119, 411119, 311119141, 311114119131141191, 611113214219231241291, 311212113114119221123124129131132141142161191192, 911512313314116319521122123124129431132341142161291292

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

OFFSET

0,1

COMMENTS

a(16) is the first term containing a zero; this is due to the fact that a(15) is the first term having exactly 10 occurrences of a two-digit number, namely 10 x 51.

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) = 19: 1 x 19 --> a(1) = 119;

a(1) = 119: 1 x 11 and 1 x 19 --> a(2) = 111119;

a(2) = 111119: 4 x 11 and 1 x 19 --> a(3) = 411119;

a(3) = 411119: 3 x 11, 1 x 19 and 1 x 41 --> a(4) = 311119141.

PROG

(Haskell) -- See Link.