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A063640
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Primes of form p*q*r + 1, where p, q and r are primes.
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4
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13, 19, 29, 31, 43, 53, 67, 71, 79, 103, 131, 139, 149, 173, 191, 223, 239, 269, 283, 293, 311, 317, 367, 389, 419, 431, 439, 443, 499, 509, 557, 599, 607, 619, 643, 647, 653, 659, 683, 743, 773, 787, 797, 823, 827, 907, 947, 971, 1031, 1039, 1087, 1091
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Also semiprimes of the form (p-1)/2 where p is a prime. - Robert G. Wilson v Sep 01 2007.
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,1000
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MATHEMATICA
| Take[ Select[ Union@ Flatten@ Table[ Prime@p*Prime@q*Prime@r + 1, {p, 48}, {q, p}, {r, q}], PrimeQ@ # &], 53] (* Or *)
semiPrimeQ[x_] := Plus @@ Last /@ FactorInteger[x] == 2; Select[Prime@ Range@ 182, semiPrimeQ[(# - 1)/2] &] (* Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 01 2007 *)
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PROG
| (PARI) { n=0; for (m=1, 10^9, p=prime(m); if (bigomega(p - 1) == 3, write("b063640.txt", n++, " ", p); if (n==1000, break)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Aug 26 2009]
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CROSSREFS
| Cf. A014612, A063639.
Sequence in context: A109902 A058898 A123840 * A092104 A094105 A073620
Adjacent sequences: A063637 A063638 A063639 * A063641 A063642 A063643
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KEYWORD
| nonn
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jul 21 2001
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