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A158724
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Numbers n such that prime(n)^2 + 1 is a semiprime.
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0
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2, 3, 5, 8, 10, 17, 18, 20, 22, 26, 32, 34, 42, 46, 58, 70, 75, 80, 87, 89, 98, 104, 105, 115, 116, 121, 131, 133, 142, 152, 158, 167, 173, 175, 177, 180, 182, 189, 190, 193, 194, 218, 228, 232, 237, 239, 242, 267, 271, 280, 282, 291, 296, 326, 333, 337, 339, 347
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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lst={}; Do[If[Plus@@Last/@FactorInteger[Prime[n]^2+1]==2, AppendTo[lst, n]], {n, 0, 6!}]; lst
Select[Range[400], PrimeOmega[Prime[#]^2+1]==2&] (* Harvey P. Dale, Jun 14 2011 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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