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Search: id:A108184
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| A108184 |
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a(n) = smallest prime such that a(n)+2n is also prime and such that a(n)<a(n+1). |
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+0
2
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| 2, 3, 7, 11, 23, 31, 41, 47, 67, 71, 83, 109, 113, 131, 139, 149, 167, 193, 197, 233, 241, 251, 263, 271, 283, 317, 331, 347, 353, 373, 379, 401, 439, 443, 479, 487, 491, 503, 523, 541, 563, 571, 577, 587, 613, 619, 641, 727, 733, 761, 787, 809, 863, 877, 883
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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Increasing primes p such that p + 2n is prime.
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EXAMPLE
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a(0)=2 since 2+0=2 is prime; a(1)=3 since 3+2=5 is prime.
a(2)=7 since 7+4=11 is prime; 5 is not in the sequence since 5+4=9 is not prime.
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MAPLE
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A108184 := proc(n) option remember; if n = 1 then 3; else for a from procname(n-1)+1 do if isprime(a) and isprime(a+2*n) then RETURN(a) ; fi; od: fi; end: seq(A108184(n), n=1..100) ; [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 31 2009]
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CROSSREFS
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Cf. A020483
Sequence in context: A126755 A034795 A165318 this_sequence A049091 A039787 A129940
Adjacent sequences: A108181 A108182 A108183 this_sequence A108185 A108186 A108187
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KEYWORD
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easy,nonn
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AUTHOR
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Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Jun 28 2005
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EXTENSIONS
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Edited and extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jul 07 2005
Edited by N. J. A. Sloane (njas(AT)research.att.com), Feb 11 2009 at the suggestion of R. J. Mathar
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