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Search: id:A092109
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| A092109 |
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Primes p such that p+3 is a semiprime. |
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+0
22
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| 3, 7, 11, 19, 23, 31, 43, 59, 71, 79, 83, 103, 131, 139, 163, 191, 199, 211, 223, 251, 271, 311, 331, 359, 379, 383, 419, 443, 463, 479, 499, 523, 563, 619, 631, 659, 691, 743, 839, 859, 863, 883, 911, 919, 971, 1039, 1091, 1123, 1151, 1171, 1223, 1231, 1259
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Primes p such that p-3 is semiprime are in A089531; n and 2n+3 both prime, A023204; 2*A063908(n)-3=A092109(n); n, 2n-3 and 2n+3 prime, A092110.
Such primes p that (p+3)/2 is prime. All these primes are congruent to 3 mod 4. [From Artur Jasinski (grafix(AT)csl.pl), Oct 11 2008]
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FORMULA
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a(n)=2*A063908(n)-3;
A092109(n)=4*A115334(n)+3 [From Artur Jasinski (grafix(AT)csl.pl), Oct 11 2008]
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MATHEMATICA
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aa = {}; k = 3; Do[If[PrimeQ[(k + Prime[n])/2], AppendTo[aa, Prime[n]]], {n, 1, 100}]; aa [From Artur Jasinski (grafix(AT)csl.pl), Oct 11 2008]
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CROSSREFS
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Cf. A023204, A089531, A063908, A092110.
A115334 [From Artur Jasinski (grafix(AT)csl.pl), Oct 11 2008]
Sequence in context: A080978 A160216 A002145 this_sequence A117991 A118260 A018805
Adjacent sequences: A092106 A092107 A092108 this_sequence A092110 A092111 A092112
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KEYWORD
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easy,nonn
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), Feb 21 2004
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