A171773 This sequence is a relative of the audioactive sequences. We generate it by starting with a symbol * and describe sequentially: *, 1*, 111*, 311*, 13211*,...

1, 111, 311, 13211, 111312211, 31131122211, 1321132132211, 111312211312111322211, 3113112221131112311332211, 13211321322113311213212322211, 1113122113121113222123211211131211121332211, 3113112221131112311332111213122112311311123112112322211

Offset

1,2

Comments

The interest of this is that if A_{n} is the n-th term of this sequence then A_{n} is a truncate of A_{n+3}. Thus the sequence gives rise to a triple A,B,C of infinite sequences of 1,2,3 such that B describes A, C describes B and A describes C.

This sequence serves as the initial portion of A001155, A001140, A001141, A001143, A001145, A001151, and A001154, as it is those sequences with the 'seed value' removed. - James E Davis, Apr 28 2016

Links

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

Formula

Each term can be found by doing a look-and-say on the previous term and appending a 1. - James E Davis, Apr 28 2016

Example

The term after 311 is one-three, two-one, one: i.e. 13211. - James E Davis, Apr 28 2016

Mathematica

NestList[FromDigits@ Append[Flatten@ Map[{Length@ #, First@ #} &, Split@ IntegerDigits@ #], 1] &, 1, 10] (* Michael De Vlieger, Apr 28 2016 *)

Crossrefs

Cf. A005150, A001155, A001140, A001141, A001143, A001145, A001151, and A001154

Sequence in context: A029486 A097650 A271312 * A349951 A244857 A225329

Adjacent sequences: A171770 A171771 A171772 * A171774 A171775 A171776

Keyword

nonn,base

Author

Louis Hirsch Kauffman (kauffman(AT)uic.edu), Dec 18 2009

Extensions

More terms from James E Davis, Apr 28 2016

Status

approved