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A198277
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a(n) is the smallest prime such that exactly n prime pairs (p,q) exist with a(n) = p * q + p + q.
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4
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2, 11, 23, 71, 239, 719, 2879, 5039, 1439, 10079, 37799, 126719, 55439, 110879, 181439, 191519, 166319, 635039, 514079, 665279, 1330559, 907199, 3243239, 831599, 2948399, 6320159, 4989599, 15301439, 14137199, 5266799, 11531519, 8315999, 23284799, 17463599, 45208799, 52390799, 34594559, 111767039, 95633999, 117976319, 70685999, 68468399
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OFFSET
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0,1
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COMMENTS
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LINKS
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PROG
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(Haskell)
import Data.List (elemIndex)
import Data.Maybe (fromJust)
a198277 n = a000040 . (+ 1) . fromJust $ elemIndex n a067432_list
(PARI) ct(n)=sumdiv(n+1, d, if(d^2>n, 0, isprime(d-1)&&isprime(n\d)))
v=vector(60); forprime(p=2, 1e9, t=ct(p); if(t && !v[t], v[t]=p; print(t" "p))); v \\ with 0's for unknown; Charles R Greathouse IV, Jul 24 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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