A121808 Say what you see in previous term, reporting each digit encountered followed by frequency.

1, 11, 12, 1121, 1321, 122131, 132231, 122232, 112431, 13213141, 14213241, 13223142, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241, 12233241

Offset

1,2

Links

Table of n, a(n) for n=1..22.

Formula

Constant at 12233241 after 13 terms.

Example

To get the term after 13213141, we say: four 1's, one 2, two 3's, one 4; therefore 14213241 (digit named before frequency).

Mathematica

RunLengthEncode[ x_List ] := (Through[ {First, Length}[ #1 ] ] &) /@ Split@ Sort@x; LookAndSay[ n_, d_:1 ] := NestList[ Flatten[ Reverse /@ RunLengthEncode[ # ] ] &, {d}, n - 1 ]; F[ n_ ] := LookAndSay[ n, 1 ][ [ n ] ]; Table[ FromDigits[ F[ n ] ], {n, 1, 15} ] (* Robert G. Wilson v Sep 11 2006 *)

Crossrefs

Another variant of A005150, A005151, A063850, etc.

Sequence in context: A042731 A087304 A340204 * A160265 A007651 A022481

Adjacent sequences: A121805 A121806 A121807 * A121809 A121810 A121811

Keyword

base,easy,nonn

Author

Ross Presser (rpresser(AT)gmail.com), Sep 09 2006

Status

approved