

A022303


The sequence a of 1's and 2's starting with (1,2,1) such that a(n) is the length of the (n+2)nd run of a.


11



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

1,2


LINKS

Clark Kimberling, Table of n, a(n) for n = 1..20000


EXAMPLE

a(1) =1, so the 3rd run has length 1, so a(4) must be 2.
a(2) = 2, so the 4th run has length 2, so a(5) = 2 and a(6) = 1.
a(3) = 1, so the 5th run has length 1, so a(7) = 2.
a(4) = 2, so the 6th run has length 2, so a(8) = 1 and a(9) = 1.
Globally, the runlength sequence of a is 1,1,1,2,1,2,2,1,2,2,1,1,2,1,...., and deleting the first two terms leaves a = A022303.


MATHEMATICA

a = {1, 2}; Do[a = Join[a, ConstantArray[If[Last[a] == 1, 2, 1], {a[[n]]}]], {n, 100}]; a (* Peter J. C. Moses, Apr 02 2016 *)


CROSSREFS

Cf. A022300, A006928, A000002.
Sequence in context: A308186 A107362 A166332 * A113189 A143098 A225515
Adjacent sequences: A022300 A022301 A022302 * A022304 A022305 A022306


KEYWORD

nonn


AUTHOR

Clark Kimberling


EXTENSIONS

Clarified and augmented by Clark Kimberling, Apr 02 2016


STATUS

approved



