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A234499
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Primes of the form (p*q*r*s - 1)/2, where p, q, r,s are distinct primes.
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4
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577, 997, 1567, 1627, 1657, 2467, 2557, 2593, 3391, 3517, 3547, 3607, 3697, 3727, 3877, 4231, 4273, 4357, 4933, 5167, 5227, 5347, 5407, 5527, 5857, 5869, 6121, 6451, 7297, 7417, 7927, 8053, 8179, 8389, 8431, 8521, 8627, 8677, 9091, 9397, 9439, 9547, 9613
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OFFSET
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1,1
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LINKS
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EXAMPLE
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MATHEMATICA
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t = Select[Range[1, 20000, 2], Map[Last, FactorInteger[#]] == Table[1, {4}] &]; Take[(t - 1)/2, 120] (* A234105 *)
v = Flatten[Position[PrimeQ[(t - 1)/2], True]] ; w = Table[t[[v[[n]]]], {n, 1, Length[v]}] (* A234498 *)
Module[{upto=10000, maxp}, maxp=Ceiling[PrimePi[upto/30]]; Select[Sort[ Select[ (#-1)/2&/@Times@@@Subsets[Prime[Range[maxp]], {4}], PrimeQ]], #<=upto&]] (* Harvey P. Dale, Feb 07 2016 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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