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Search: id:A117931
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| A117931 |
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Inductive sum-and-difference sequence. |
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+0
3
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| 1, 2, 7, 5, 9, 3, 10, 4, 14, 6, 19, 8, 23, 11, 25, 12, 28, 13, 31, 15, 33, 16, 35, 17, 38, 18, 41, 20, 43, 21, 46, 22, 50, 24, 53, 26, 56, 27, 59, 29, 62, 30, 66, 32, 70, 34, 73, 36, 76, 37, 79, 39, 82, 40, 86, 42, 89, 44, 92, 45, 95, 47, 97, 48, 100, 49, 103, 51, 106, 52, 109
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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A permutation of the natural numbers.
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FORMULA
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a(1)=1, a(2)=2, and for n>=3 let F(n)={a(1),a(2),...,a(n)}. For odd n>=3, a(n)=x+y where x,y are the least positive integers not in F(n-1); for even n>=3, a(n)=least positive difference x-y such that x,y are in F(n-1) and x-y is not in F(n-1).
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EXAMPLE
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a(3)=3+4, a(4)=7-2, a(4)=3+6, a(5)=5-2, a(6)=4+6.
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CROSSREFS
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Cf. A117932, A117933.
Sequence in context: A097157 A079833 A010593 this_sequence A011051 A024691 A135076
Adjacent sequences: A117928 A117929 A117930 this_sequence A117932 A117933 A117934
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KEYWORD
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nonn
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AUTHOR
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Clark Kimberling (ck6(AT)evansville.edu), Apr 03 2006
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