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A two-digit Look-and-Say sequence starting with 11: each term summarizes the increasing two-digit substrings of the previous term.
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%I #17 Aug 23 2024 21:15:08

%S 11,111,211,111121,311112121,311212221131,211212113221222231,

%T 211312113421422123131132,311212413114421122123331132134242,

%U 411412313114421122123224331132233134141342144,411312413414321322323124431232233234441242143244

%N A two-digit Look-and-Say sequence starting with 11: each term summarizes the increasing two-digit substrings of the previous term.

%C 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 31.

%H Reinhard Zumkeller, <a href="/A209233/b209233.txt">Table of n, a(n) for n = 0..1000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/LookandSaySequence.html">Look and Say Sequence</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Look-and-say_sequence">Look-and-say sequence</a>

%H Reinhard Zumkeller, <a href="/A209234/a209234.hs.txt">Haskell program for two-digit Look-and-Say sequences</a>

%e a(0) = 11: 1 x 11 --> a(1) = 111;

%e a(1) = 111: 2 x 11 --> a(2) = 211;

%e a(2) = 211: 1 x 11 and 1 x 21 --> a(3) = 111121;

%e a(3) = 111121: 3 x 11, 1 x 12 and 1 x 21 --> a(4) = 311112121.

%o (Haskell) -- See Link.

%Y Cf. A005151, A047842.

%Y Cf. A209234 (start=10), A221368 (start=12), A221369 (start=13), A221372 (start=19), A221373 (start=99).

%K nonn,base

%O 0,1

%A _Reinhard Zumkeller_, Jan 13 2013