perl -E'$_=1;while(++$t<19){say;my@a;push@a,length$1,$2 while/((\d)\2*)/g;$_=join"",@a}'

##</code><code>##

perl -E'for(0..19){say$_=$t//1;$t="";$t.=(length$1).$2 while/((.)\2*)/g}'