

A092434


Number of words X=x(1)x(2)x(3)...x(n) of length n in three digits {0,1,2} that are invariant under the mapping X > Y, where y(i)=((AD)^(i1))x(1) and where (AD) denotes the absolute difference (AD)x(i)=abs(x(i+1)x(i)) (in other words, y(i) is the ith element in the diagonal of leading entries in the table of absolute differences of {x(1), x(2),...,x(n)).


0



3, 4, 10, 12, 28, 32, 72, 80, 176, 192, 416, 448, 960, 1024
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OFFSET

1,1


COMMENTS

In the two digits {0,1} the corresponding sequence is 2,2,4,4,8,8,16,16,32,32,64,64,... which appears to be A060546.


LINKS

Table of n, a(n) for n=1..14.


FORMULA

It is conjectured that a(n)=(n+2)*2^((n1) div 2).


EXAMPLE

The table of absolute differences of {2,1,1,0} is
2
1.1
1.0.1
0.1.1.0
with the diagonal of leading absolute differences again forming the word (2110).
Thus (2110) is one of the twelve words in the digits {0,1,2} that are counted in calculating a(4).


CROSSREFS

Cf. A060546.
Sequence in context: A259559 A050187 A101506 * A239632 A031367 A073443
Adjacent sequences: A092431 A092432 A092433 * A092435 A092436 A092437


KEYWORD

nonn


AUTHOR

John W. Layman, Mar 23 2004


STATUS

approved



