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Search: id:A096784
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| A096784 |
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Numbers n such that both n and n+1 are composite numbers that sum up to a prime. |
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+0
12
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| 8, 9, 14, 15, 20, 21, 26, 33, 35, 39, 44, 48, 50, 51, 54, 56, 63, 65, 68, 69, 74, 75, 81, 86, 90, 95, 98, 99, 105, 111, 114, 116, 119, 120, 125, 128, 134, 135, 140, 141, 146, 153, 155, 158, 165, 168, 174, 176, 183, 186, 189, 194, 200, 204, 209, 215, 216, 219, 221
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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Equals (A060254 -1)/2.
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MATHEMATICA
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Select[ Range[ 225], PrimeQ[ # ] == PrimeQ[ # + 1] == False && PrimeQ[2# + 1] == True &] (from Robert G. Wilson v Jul 11 2004)
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PROGRAM
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(PARI) nextcomposite(k)=if(k<3, 4, if(isprime(k), k+1, k));
{m=230; n=4; while(n<m, k=nextcomposite(n+1); p=n+k; if(k==n+1&&isprime(p), print1(n, ", ")); n=k)} - Klaus Brockhaus, Jul 11 2004
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CROSSREFS
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See A060254 for the primes 2n+1.
Cf. A096785, A096786, A096787, A096788.
Sequence in context: A105741 A083134 A068780 this_sequence A059869 A105833 A114305
Adjacent sequences: A096781 A096782 A096783 this_sequence A096785 A096786 A096787
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KEYWORD
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nonn
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AUTHOR
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Lekraj Beedassy (blekraj(AT)yahoo.com), Jul 09 2004
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EXTENSIONS
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Corrected and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Ray Chandler (rayjchandler(AT)sbcglobal.net), Jul 10 2004
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