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A119835
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Primes p such that 2*p#-1 and 2*p#+1 are twin primes.
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2
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..6.
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EXAMPLE
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2*2-1=3 2*2+1=5, 3 and 5 twin primes so a(1)=2;
2*2*3-1=11 2*2*3+1=13, 11 and 13 twin primes so a(2)=3;
2*2*3*5-1=59 2*2*3*5+1=61, 59 and 61 twin primes so a(3)=5.
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MAPLE
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isA001359 := proc(n) RETURN(isprime(n) and isprime(n+2)); end: primo := 2 : print(primo); for n from 2 to 20000 do p := ithprime(n); primo := primo*p; if isA001359(2*primo-1) then print(p); fi; od : # R. J. Mathar, Aug 09 2006
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PROG
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(Magma) p:p in PrimesUpTo(4000)|IsPrime(2*&*PrimesUpTo(p)-1) and IsPrime(2*&*PrimesUpTo(p)+1)]; // Marius A. Burtea, Mar 25 2019
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CROSSREFS
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Cf. A119833, A119834.
Sequence in context: A006341 A086107 A046713 * A076609 A117059 A117058
Adjacent sequences: A119832 A119833 A119834 * A119836 A119837 A119838
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KEYWORD
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more,nonn
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AUTHOR
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Pierre CAMI, May 25 2006
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STATUS
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approved
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