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Search: id:A128286
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| A128286 |
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a[n]= is the n-th smallest product of 5 odd primes m=p1*p2*p3*p4*p5, such that (d+m/d)/2 are all primes for each d dividing m. |
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5
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| 884037, 1137565, 2398377, 123156993, 681714273, 2347722213, 7283144845, 7794246057, 8953447917, 10287992785, 13749228493, 38108016453, 38901676405, 70918253385, 71809744693, 120418624965, 148282565865, 150721729873
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a[6]>10^9
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EXAMPLE
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eg 884037 = 3*7*11*43*89 and (1+884037)/2, (3+7*11*43*89)/2,
(7+3.11.43.89)/2, (11+3.7.43.89)/2, (43+3.7.11.89)/2, (89+3.7.11.43)/2,
(3.7+11.43.89)/2, (3.11+7.43.89)/2, (3.43+7.11.89)/2,(3.89+7.11.43)/2,
(7.11+3.43.89)/2, (7.43+3.7.89)/2, (7.89+3.7.43)/2, (11.43+3.7.89)/2,
(11.89+3.7.43)/2, (43*89+3*7*11)/2 are all primes and 884037 is the smallest such integer, so a[1]=884037
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CROSSREFS
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Cf. A128281, A005383, A128283, A128284, A128285.
Sequence in context: A115546 A166485 A034609 this_sequence A092016 A105379 A032429
Adjacent sequences: A128283 A128284 A128285 this_sequence A128287 A128288 A128289
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KEYWORD
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hard,nonn
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AUTHOR
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Kok Seng Chua (chuakokseng(AT)hotmail.com), Mar 05 2007
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EXTENSIONS
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a(6)-a(18) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Oct 12 2008
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