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A085722
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Numbers k such that k^2 + 1 is a semiprime.
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38
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3, 5, 8, 9, 11, 12, 15, 19, 22, 25, 28, 29, 30, 34, 35, 39, 42, 44, 45, 46, 48, 49, 50, 51, 52, 58, 59, 60, 61, 62, 64, 65, 69, 71, 76, 78, 79, 80, 85, 86, 88, 92, 95, 96, 100, 101, 102, 104, 106, 108, 114, 121, 131, 136, 139, 140, 141, 144, 145, 152, 154, 158, 159, 164
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OFFSET
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1,1
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COMMENTS
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Corresponding semiprimes k^2+1 are in A144255.
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LINKS
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FORMULA
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MATHEMATICA
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Select[Range[200], PrimeOmega[#^2+1]==2&] (* Harvey P. Dale, Feb 28 2013 *)
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PROG
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(PARI) select(vector(50, n, n), n->bigomega(n^2+1)==2)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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