

A270648


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


2



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

1,1


COMMENTS

See A270641 for a guide to related sequences.


LINKS

Clark Kimberling, Table of n, a(n) for n = 1..10000


EXAMPLE

a(1) = 2, so the 2nd run has length 2, so a(5) must be 1 and a(6) = 1.
a(2) = 2, so the 3rd run has length 2, so a(7) = 2 and a(8) = 2.
a(3) = 2, so the 4th run has length 2, so a(9) = 1 and a(10) = 1.
Globally, the runlength sequence of a is 4,2,2,2,2,1,1,2,2,1,1,2,2,1,2,1,1,2,..., and deleting the first term leaves a = A270648.


MATHEMATICA

a = {2, 2, 2, 2}; Do[a = Join[a, ConstantArray[If[Last[a] == 1, 2, 1], {a[[n]]}]], {n, 200}]; a (* Peter J. C. Moses, Apr 01 2016 *)


CROSSREFS

Cf. A000002, A006928, A022300, A270641.
Sequence in context: A275850 A112505 A104638 * A331034 A057155 A037812
Adjacent sequences: A270645 A270646 A270647 * A270649 A270650 A270651


KEYWORD

nonn,easy


AUTHOR

Clark Kimberling, Apr 07 2016


STATUS

approved



