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A111192
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Product of the n-th sexy prime pair.
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5
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55, 91, 187, 247, 391, 667, 1147, 1591, 1927, 2491, 3127, 4087, 4891, 5767, 7387, 9991, 10807, 11227, 12091, 17947, 23707, 25591, 28891, 30967, 37627, 38407, 51067, 52891, 55687, 64507, 67591, 70747, 75067, 78391, 96091, 98587, 111547, 122491
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Sexy Primes.
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FORMULA
| a(n) = A023201(n) * A046117(n). [Reinhard Zumkeller, Sep 13 2011]
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EXAMPLE
| a(2)=91 because the second sexy prime pair is (7, 13) and 7*13=91.
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MATHEMATICA
| #(#+6)&/@Select[Prime[Range[100]], PrimeQ[#+6]&] [From Harvey P. Dale, Dec. 17, 2010]
(* For checking large numbers, the following code is better. For instance, we could use the fQ function to determine that 229031718473564142083 is not in this sequence. *) fQ[n_] := Block[{fi = FactorInteger[n]}, Last@# & /@ fi == {1, 1} && Differences[ First@# & /@ fi] == {6}]; Select[ Range[125000], fQ] (* Robert G. Wilson v, Feb 08 2012 *)
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PROG
| (Haskell)
a111192 n = a111192_list !! (n-1)
a111192_list = f a000040_list where
f (p:ps@(q:r:_)) | q - p == 6 = (p*q) : f ps
| r - p == 6 = (p*r) : f ps
| otherwise = f ps
-- Reinhard Zumkeller, Sep 13 2011
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CROSSREFS
| Cf. A023201, A104229.
Cf. A037074, A143206, A195118; intersection of A143205 and A001358.
Sequence in context: A027865 A195118 A143205 * A063873 A063131 A128880
Adjacent sequences: A111189 A111190 A111191 * A111193 A111194 A111195
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KEYWORD
| nonn,changed
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AUTHOR
| Shawn M Moore (sartak(AT)gmail.com), Oct 23 2005
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