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 A171602 Lesser of two consecutive primes such that half-sums are semiprimes. 1
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..52. EXAMPLE (3+5)/2=4->2*2, (5+7)/2=6->2*3, (7+11)/2=9->3*3, (13+17)/2=15->3*5,.. MATHEMATICA 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 CROSSREFS Sequence in context: A075579 A059788 A077171 * A155189 A065384 A354217 Adjacent sequences: A171599 A171600 A171601 * A171603 A171604 A171605 KEYWORD nonn AUTHOR Vladimir Joseph Stephan Orlovsky, Dec 12 2009 STATUS approved

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Last modified August 9 08:50 EDT 2024. Contains 375035 sequences. (Running on oeis4.)