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A209233 A two-digit Look-and-Say sequence starting with 11: each term summarizes the increasing two-digit substrings of the previous term.

%I A209233 #18 Feb 16 2025 08:33:16
%S A209233 11,111,211,111121,311112121,311212221131,211212113221222231,
%T A209233 211312113421422123131132,311212413114421122123331132134242,
%U A209233 411412313114421122123224331132233134141342144,411312413414321322323124431232233234441242143244
%N A209233 A two-digit Look-and-Say sequence starting with 11: each term summarizes the increasing two-digit substrings of the previous term.
%C A209233 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 A209233 Reinhard Zumkeller, <a href="/A209233/b209233.txt">Table of n, a(n) for n = 0..1000</a>
%H A209233 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LookandSaySequence.html">Look and Say Sequence</a>
%H A209233 Wikipedia, <a href="http://en.wikipedia.org/wiki/Look-and-say_sequence">Look-and-say sequence</a>
%H A209233 Reinhard Zumkeller, <a href="/A209234/a209234.hs.txt">Haskell program for two-digit Look-and-Say sequences</a>
%e A209233 a(0) = 11: 1 x 11 --> a(1) = 111;
%e A209233 a(1) = 111: 2 x 11 --> a(2) = 211;
%e A209233 a(2) = 211: 1 x 11 and 1 x 21 --> a(3) = 111121;
%e A209233 a(3) = 111121: 3 x 11, 1 x 12 and 1 x 21 --> a(4) = 311112121.
%o A209233 (Haskell) -- See Link.
%Y A209233 Cf. A005151, A047842.
%Y A209233 Cf. A209234 (start=10), A221368 (start=12), A221369 (start=13), A221372 (start=19), A221373 (start=99).
%K A209233 nonn,base
%O A209233 0,1
%A A209233 _Reinhard Zumkeller_, Jan 13 2013