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Search: id:A132075
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| A132075 |
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An attempt to find a permutation of the positive integers with the property that for every n, a(n) is the largest number among a(1), a(2),..., a(n) that when added to a(n+1) gives a prime. |
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+0
2
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| 1, 2, 3, 4, 7, 6, 5, 14, 9, 10, 13, 16, 15, 8, 11, 20, 17, 12, 19, 24, 23, 18, 25, 22, 21, 26, 27, 34, 33, 28, 31, 30, 29, 32, 35, 36, 37, 46, 43, 40, 39, 44, 45, 38, 41, 42, 47, 50, 59, 54, 55, 58, 51, 62, 65, 48, 61, 52, 57, 56, 53, 60, 49, 64, 63, 68, 69, 70, 67, 72, 77, 80
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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The terms are found from table A088643 as follows. First write each row backwards but miss out all the terms from the middle onwards. This gives: [empty], [1], [1], [1, 2], [1, 4], [1, 4, 3], [1, 4, 3], [1, 2, 3, 4], [1, 2, 3, 4], [1, 2, 3, 4, 7] etc. Then build the sequence up by always selecting the first such truncated row that extends the terms already chosen. It is unclear whether this process can be continued indefinitely.
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CROSSREFS
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Cf. A088643.
Sequence in context: A122198 A122155 A106454 this_sequence A074846 A120225 A130685
Adjacent sequences: A132072 A132073 A132074 this_sequence A132076 A132077 A132078
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Boddington (pbotherstuff(AT)yahoo.co.uk), Oct 30 2007
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