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Search: id:A152102
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| A152102 |
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Semiprimes based on powers of two and primes: a(n)=If[PrimeQ[(2*n - 1)] && PrimeQ[(2*n + 1)], (2^(2*n - 1) - 1)*(2^(2*n + 1) + 1)]. |
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1
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| 231, 3999, 16771071, 68719083519, 1152921502996234239, 19342813113827469725532159, 1329227995784915871174424803370074111, 22300745198530623141528634722924057038159871
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Idea resulted from seqfan posts by Artur Jasinski (grafix(AT)csl.pl).
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FORMULA
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a(n)=a(n)=If[PrimeQ[(2*n - 1)] && PrimeQ[(2*n + 1)], (2^(2*n - 1) - 1)*(2^(2*n + 1) + 1)].
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MATHEMATICA
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a[n_] := If[PrimeQ[(2*n - 1)] && PrimeQ[(2*n + 1)], (2^(2*n - 1) - 1)*(2^(2*n + 1) + 1), {}]; Flatten[Table[a[n], {n, 1, 100}]]
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CROSSREFS
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Sequence in context: A117223 A160355 A029569 this_sequence A152500 A066370 A139412
Adjacent sequences: A152099 A152100 A152101 this_sequence A152103 A152104 A152105
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KEYWORD
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nonn
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AUTHOR
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Roger L. Bagula (rlbagulatftn(AT)yahoo.com), Nov 24 2008
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