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Search: id:A128280
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| A128280 |
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a(1)=2, then a(n) is the least number absent among a(1)..a(n-1) and such that a(n)+a(n-1) is prime. |
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+0
1
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| 2, 1, 4, 3, 8, 5, 6, 7, 10, 9, 14, 15, 16, 13, 18, 11, 12, 17, 20, 21, 22, 19, 24, 23, 30, 29, 32, 27, 26, 33, 28, 25, 34, 37, 36, 31, 40, 39, 44, 35, 38, 41, 42, 47, 50, 51, 46, 43, 54, 49, 48, 53, 56, 45, 52, 55, 58, 69, 62, 65, 66, 61, 70, 57, 74, 63, 64, 67, 60, 71, 68, 59
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Sequence well may be rearrangement of natural numbers. Interestingly, subsets of n first terms for n={2,4,8,10,18,22,24,56,..} are permutations of 1..n. E.g. first 56 terms: {2,1,4,3,8,5,6,7,10,9,14,15,16,13,18,11,12,17,20,21,22, 19,24,23, 30,29,32,27,26,33,28,25,34,37,36,31,40,39,44,35,38,41,42,47,50,51, 46,43,54,49,48,53,56,45,52,55} are permutation of 1..56.
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CROSSREFS
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Cf. A083236.
Sequence in context: A085930 A087207 A074987 this_sequence A106625 A008347 A112387
Adjacent sequences: A128277 A128278 A128279 this_sequence A128281 A128282 A128283
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KEYWORD
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nonn
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), May 03 2007
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