OFFSET
1,2
COMMENTS
MATHEMATICA
s[n_] := If[n == 1, {1}, s[n] = Join[s[n-1], Length /@ Split[s[n-1]]]];
a[n_] := FromDigits[s[n]];
Array[a, 9] (* Jean-François Alcover, Feb 24 2021 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
N. J. A. Sloane, Jan 31 2019
STATUS
approved