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A289250
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Primes p such that p + 4 is a semiprime.
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2
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2, 5, 11, 17, 29, 31, 47, 53, 61, 73, 83, 89, 107, 137, 139, 151, 157, 173, 179, 181, 197, 199, 211, 233, 263, 283, 317, 331, 337, 367, 373, 389, 409, 433, 443, 449, 467, 523, 541, 547, 569, 577, 587, 593, 607, 619, 631, 677, 683, 691, 709, 719, 727, 733, 751, 787, 809, 811, 827
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OFFSET
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1,1
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COMMENTS
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Except for case p=5, p+4 is never a perfect square.
For p = {2, 11, 31, 73, 139, 433, 1759, 2017} p+4 is a product of two consecutive primes.
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LINKS
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EXAMPLE
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2+4=6=2*3, 5+4=9=3*3, 11+4=15=3*5 (all semiprimes).
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MATHEMATICA
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PROG
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(PARI) issemi(n)=bigomega(n)==2
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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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