

A088203


Infinite audioactive word that shifts 1 place left under "Look and Say" method A, starting with a(1)=2.


7



2, 1, 2, 1, 1, 1, 2, 3, 1, 1, 2, 1, 3, 2, 1, 1, 2, 1, 1, 1, 3, 1, 2, 2, 1, 1, 2, 3, 1, 1, 3, 1, 1, 2, 2, 2, 1, 1, 2, 1, 3, 2, 1, 1, 3, 2, 1, 3, 2, 2, 1, 1, 2, 1, 1, 1, 3, 1, 2, 2, 1, 1, 3, 1, 2, 1, 1, 1, 3, 2, 2, 2, 1, 1, 2, 3, 1, 1, 3, 1, 1, 2, 2, 2, 1, 1, 3, 1, 1, 1, 2, 3, 1, 1, 3, 3, 2, 2, 1, 1, 2, 1, 3, 2, 1
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OFFSET

1,1


COMMENTS

A006751(n) = concatenation of nth row.  Reinhard Zumkeller, Aug 09 2012
From JeanChristophe HervĂ©, May 07 2013: (Start)
The sequence is obtained continuously by applying the lookandsay rule from seed 2: 2 > 1,2 > 1,1,1,2 > etc. The sequence is then determined by pairs of digits. Terms of even ranks are counts while odd ranks are figures. A225224 and A221646 are from seed 1 and A088204 from seed 3.
The present sequence is the concatenation of A006751 (original lookandsay method by blocks) because, with seed 2, all blocks of A006751 begin with 1 or 3 and end with 2 and therefore, there is no possible interaction between blocks after concatenation. (end)


REFERENCES

J. H. Conway, The weird and wonderful chemistry of audioactive decay, in T. M. Cover and Gopinath, eds., Open Problems in Communication and Computation, Springer, NY 1987, pp. 173188.


LINKS

Reinhard Zumkeller, Rows n = 1..25 of triangle, flattened
Kevin Watkins, Abstract Interpretation Using Laziness: Proving Conway's Lost Cosmological Theorem,
Kevin Watkins, Proving Conway's Lost Cosmological Theorem, POP seminar talk, CMU, Dec 2006
Eric W. Weisstein, MathWorld: Look and Say Sequence
Wikipedia, Lookandsay sequence


PROG

(Haskell) see Watkins link, p. 3.
import Data.List (group)
a088203 n k = a088203_tabf !! (n1) !! (k1)
a088203_row n = a088203_tabf !! (n1)
a088203_tabf = iterate
(concat . map (\xs > [length xs, head xs]) . group) [2]
 Reinhard Zumkeller, Aug 09 2012


CROSSREFS

Cf. A088204, A087282, A005150.
Cf. A034002, A005150, A006751
Cf. A225224, A221646 (seed one).
Sequence in context: A302790 A140816 A029433 * A205649 A176510 A061342
Adjacent sequences: A088200 A088201 A088202 * A088204 A088205 A088206


KEYWORD

nonn,easy,tabf


AUTHOR

Paul D. Hanna, Sep 22 2003


STATUS

approved



