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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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MATHEMATICA
| 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&] (* From Harvey P. Dale, June 14 2011 *)
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PROG
| (PARI) n=0; forprime(p=2, 1e4, n++; if(bigomega(p^2+1)==2, print1(n", "))) \\ Charles R Greathouse IV, Jun 14 2011
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CROSSREFS
| Sequence in context: A022955 A087279 A084907 * A181100 A036961 A122633
Adjacent sequences: A158721 A158722 A158723 * A158725 A158726 A158727
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KEYWORD
| nonn
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AUTHOR
| Vladimir Orlovsky (4vladimir(AT)gmail.com), Mar 24 2009
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