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Search: id:A123754
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| A123754 |
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Positive numbers of the form 4*n^2-1 which are not semiprimes. |
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1
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| 3, 63, 99, 195, 255, 399, 483, 575, 675, 783, 1023, 1155, 1295, 1443, 1599, 1935, 2115, 2303, 2499, 2703, 2915, 3135, 3363, 3843, 4095, 4355, 4623, 4899, 5475, 5775, 6083, 6399, 6723, 7055, 7395, 7743, 8099, 8463, 8835, 9215, 9603, 9999, 10815
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Positive numbers of the form 4*n^2-1 which are semiprimes can be found in A037074.
Or, all positive products of the form A014076(i)*[A014076(i)+-2], duplicates removed. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 08 2007
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FORMULA
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( A000466 MINUS {-1} ) MINUS A001358. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 08 2007
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MATHEMATICA
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Select[4*(Range[54])^2-1, Not[PrimeQ[Sqrt[(#+ 1)]-1] && PrimeQ[Sqrt[(#+1)]+1]]&]
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CROSSREFS
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Cf. A000466, A037074.
Sequence in context: A104403 A135444 A087886 this_sequence A048354 A046181 A120053
Adjacent sequences: A123751 A123752 A123753 this_sequence A123755 A123756 A123757
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KEYWORD
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nonn
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AUTHOR
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Roger Bagula (rlbagulatftn(AT)yahoo.com), Nov 16 2006
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EXTENSIONS
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Edited by njas, Aug 03 2007
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