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A087859
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a(n) = the number of twin primes x-1,x+1 such that x=j*(p(n)#)/p(k), where 1<=j<p(n+1) and 1<=k<=n and p(k) doesn't divide j.
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2
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0, 1, 3, 7, 8, 10, 15, 13, 13, 15, 10, 12, 15, 15, 18, 13, 22, 15, 23, 19, 23, 16, 19, 16, 22, 13, 15, 20, 23, 14, 18, 27, 20, 20, 16, 25, 21, 25, 14, 27, 21
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| p(n) is the n-th prime; # denotes primorial (A002110).
a(n) seems to grow like 4 log p(n).
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EXAMPLE
| a(3)=3 because for j,k=(1,3),(2,3),(3,3), j*(5#)/p(k)+-1 are primes.
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CROSSREFS
| Cf. A002110, A087941, A088968.
Sequence in context: A019270 A047357 A003607 * A050010 A106753 A174871
Adjacent sequences: A087856 A087857 A087858 * A087860 A087861 A087862
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KEYWORD
| nonn
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AUTHOR
| Pierre CAMI (colettecami(AT)aol.com), Oct 25 2003
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EXTENSIONS
| Edited by Don Reble (djr(AT)nk.ca), Nov 16 2005
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