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Search: id:A084920
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| A084920 |
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(prime(n)-1)*(prime(n)+1). |
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+0
9
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| 3, 8, 24, 48, 120, 168, 288, 360, 528, 840, 960, 1368, 1680, 1848, 2208, 2808, 3480, 3720, 4488, 5040, 5328, 6240, 6888, 7920, 9408, 10200, 10608, 11448, 11880, 12768, 16128, 17160, 18768, 19320, 22200, 22800, 24648, 26568, 27888, 29928
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(n)=A006093(n)*A008864(n);
a(n)=A084921(n)*2 for n>1; a(n)=A084922(n)*6 for n>2.
a(n)=prime(n)^2-1. [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Oct 17 2009]
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FORMULA
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product_{n=1,2,..infinity} a(n)/A066872(n) = 2/5. a(n) = A001248(n)-1. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 01 2009]
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MATHEMATICA
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f[n_]:=Prime[n]^2-1; lst={}; Do[AppendTo[lst, f[n]], {n, 5!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Oct 17 2009]
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CROSSREFS
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Cf. A000040, A005563.
Sequence in context: A065083 A037450 A081990 this_sequence A026556 A096001 A080097
Adjacent sequences: A084917 A084918 A084919 this_sequence A084921 A084922 A084923
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 11 2003
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