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Search: id:A090905
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| A090905 |
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Group the natural numbers such that the n-th group product is a multiple of the (n-1)th group product. (1), (2),(3,4), (5,6,7,8),(9,10,11,12,13,14),(15,16,17,18,19,20,21,22,23,24,25,26),... Sequence contains the first term of each group. |
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5
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| 1, 2, 3, 5, 9, 15, 27, 47, 87, 167, 327, 635, 1263, 2519, 5007, 10007, 19947, 39875, 79739, 159399, 318779, 637503, 1274999, 2549979, 5099903, 10199787, 20399535, 40799063, 81598083, 163196135, 326392259, 652784499, 1305568943, 2611137839
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OFFSET
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1,2
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COMMENT
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Conjecture: For n > 4 the last term of the n-th group is 2p where p is the largest prime in the (n-1)th group. And these are the Bertrand primes.
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CROSSREFS
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Cf. A090904, A090906, A090907.
Sequence in context: A065954 A067847 A022858 this_sequence A065956 A060013 A092424
Adjacent sequences: A090902 A090903 A090904 this_sequence A090906 A090907 A090908
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Dec 13 2003
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EXTENSIONS
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More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Feb 10 2006
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