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A120638
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Primes such that their triple is not 2 away from a prime number.
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0
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2, 31, 41, 73, 101, 107, 109, 131, 151, 157, 179, 223, 229, 241, 281, 283, 311, 359, 379, 389, 421, 449, 463, 509, 521, 547, 563, 571, 599, 613, 617, 619, 631, 641, 647, 653, 661, 683, 691, 701, 719, 733, 739, 743, 773, 787, 809, 811, 821, 827, 829, 839, 857
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| This sequence is a variation of the sequence in the reference. However, this sequence should have an infinite number of terms. k=2 in the PARI code.
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REFERENCES
| R. Crandall and C. Pomerance, Prime Numbers A Computational Perspective, Springer Verlag 2002, p. 49, exercise 1.18.
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EXAMPLE
| 31*3 = 93 which is two away from 91 and 95 both not prime.
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MATHEMATICA
| Select[Prime@Range@200, !PrimeQ[3#-2]&&!PrimeQ[3#+2]&] (* From Vladimir Joseph Stephan Orlovsky, Apr 25 2011 *)
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PROG
| (PARI) primepm3(n, k) = =number of iterations, k = factor { local(x, p1, p2, f1, f2, r); if(k%2, r=2, r=1); for(x=1, n, p1=prime(x); p2=prime(x+1); if(!isprime(p1*k+r)&!isprime(p1*k-r), print1(p1", ") ) ) }
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CROSSREFS
| Cf. A023208, A088878, A125272.
Sequence in context: A020896 A042153 A102630 * A101017 A193423 A129900
Adjacent sequences: A120635 A120636 A120637 * A120639 A120640 A120641
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KEYWORD
| easy,nonn
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AUTHOR
| Cino Hilliard (hillcino368(AT)gmail.com), Aug 17 2006
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