This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A221372 #11 Feb 16 2025 08:33:19 %S A221372 19,119,111119,411119,311119141,311114119131141191, %T A221372 611113214219231241291, %U A221372 311212113114119221123124129131132141142161191192,911512313314116319521122123124129431132341142161291292 %N A221372 A two-digit Look-and-Say sequence starting with 19: each term summarizes the increasing two-digit substrings of the previous term. %C A221372 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. %H A221372 Reinhard Zumkeller, <a href="/A221372/b221372.txt">Table of n, a(n) for n = 0..1000</a> %H A221372 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LookandSaySequence.html">Look and Say Sequence</a> %H A221372 Wikipedia, <a href="http://en.wikipedia.org/wiki/Look-and-say_sequence">Look-and-say sequence</a> %H A221372 Reinhard Zumkeller, <a href="/A209234/a209234.hs.txt">Haskell program for two-digit Look-and-Say sequences</a> %e A221372 a(0) = 19: 1 x 19 --> a(1) = 119; %e A221372 a(1) = 119: 1 x 11 and 1 x 19 --> a(2) = 111119; %e A221372 a(2) = 111119: 4 x 11 and 1 x 19 --> a(3) = 411119; %e A221372 a(3) = 411119: 3 x 11, 1 x 19 and 1 x 41 --> a(4) = 311119141. %o A221372 (Haskell) -- See Link. %Y A221372 Cf. A005151, A047842. %Y A221372 Cf. A209234 (start=10), A209233 (start=11), A221368 (start=12), A221369 (start=13), A221373 (start=99). %K A221372 nonn,base %O A221372 0,1 %A A221372 _Reinhard Zumkeller_, Jan 13 2013