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A143206
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Product of the n-th cousin prime pair.
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4
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21, 77, 221, 437, 1517, 2021, 4757, 6557, 9797, 11021, 12317, 16637, 27221, 38021, 50621, 53357, 77837, 95477, 99221, 123197, 145157, 159197, 194477, 210677, 216221, 239117, 250997, 378221, 416021, 455621, 549077, 576077, 594437, 680621
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| a(n) = A023200(n)*A046132(n);
intersection of A143203 and A001358.
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Cousin Primes
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EXAMPLE
| a(1) = 3*7 = 3*(3+4) = 21;
a(2) = 7*11 = 7*(7+4) = 77;
a(3) = 13*17 = 13*(13+4) = 221;
a(4) = 19*23 = 19*(19+4) = 437.
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MATHEMATICA
| fQ[n_] := Block[{fi = FactorInteger@ n}, Last@# & /@ fi == {1, 1} && Differences[ First@# & /@ fi] == {4}]; Select[ Range@ 700000, fQ] (* Robert G. Wilson v, Feb 08 2012 *)
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PROG
| (Haskell)
a143206 n = a143206_list !! (n-1)
a143206_list = (3*7) : f a000040_list where
f (p:ps@(p':_)) | p'-p == 4 = (p*p') : f ps
| otherwise = f ps
-- Reinhard Zumkeller, Sep 13 2011
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CROSSREFS
| Cf. A037074, A111192.
Sequence in context: A109357 A082041 A085027 * A182754 A045559 A144314
Adjacent sequences: A143203 A143204 A143205 * A143207 A143208 A143209
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KEYWORD
| nonn,changed
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 12 2008
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