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A138651
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Number of distinct values obtained when each of the operators # in the expression 1#2#3#...#n is replaced by + (add) or x (multiply) in all possible ways, for n=1,2,3,...
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0
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1, 2, 3, 7, 14, 26, 52, 104, 201, 379, 751, 1422, 2679, 5068, 9383, 17249
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| For n=4, the eight expressions {1+2+3+4,1+2+3x4,1+2x3+4,1+2x3x4,1x2+3+4,1x2+3x4, 1x2x3+4,1x2x3x4} are obtained, with the eight values {10,15,11,25,9,14,10,24} respectively, seven of which are distinct, so a(4)=7.
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CROSSREFS
| Cf. A069765, A078389.
Sequence in context: A081941 A027957 A054194 * A131300 A078043 A131666
Adjacent sequences: A138648 A138649 A138650 * A138652 A138653 A138654
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KEYWORD
| nonn
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AUTHOR
| John W. Layman (layman(AT)math.vt.edu), May 15 2008
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