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A171602
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Lesser of two consecutive primes such that half-sums are semiprimes.
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1
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3, 5, 7, 13, 19, 23, 31, 37, 67, 83, 89, 109, 127, 131, 199, 211, 251, 271, 307, 331, 379, 383, 389, 443, 449, 467, 487, 499, 509, 563, 661, 683, 719, 769, 797, 877, 929, 937, 971, 997, 1009, 1123, 1163, 1201, 1223, 1231, 1237, 1283, 1291, 1297, 1307, 1459
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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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(3+5)/2=4->2*2, (5+7)/2=6->2*3, (7+11)/2=9->3*3, (13+17)/2=15->3*5,..
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MATHEMATICA
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f[n_]:=Last/@FactorInteger[n]=={1, 1}||Last/@FactorInteger[n]=={2}; lst={}; Do[p=Prime[n]; q=Prime[n+1]; s=(p+q)/2; If[f[s], AppendTo[lst, p]], {n, 6!}]; lst
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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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