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%I #12 May 09 2014 23:00:08
%S 0,0,2,2,0,2,3,2,5,3,2,3,5,2,3,7,5,2,7,3,2,5,5,3,3,5,2,3,2,3,7,3,3,2,
%T 3,2,3,5,5,5,7,2,13,2,19,2,3,3,3,2,7,3,2,3,3,3,3,2,3,3,2,7,5,5,2,0,13,
%U 5,3,2,3,7,7,3,3,7,5,3,3,5,5,2,7,2,3,13
%N Smallest prime p such that 2*prime(n) - p^2 is semiprime, or a(n)=0 if there is no such p.
%H Peter J. C. Moses, <a href="/A241533/b241533.txt">Table of n, a(n) for n = 1..1000</a>
%e Let n=16, then 2*prime(16) = 2*53 = 106. We have 106-4=102, 106-9=97, 106-25=81, 106-49=57, and only the last number is semiprime. So a(16)=7.
%o (PARI) a(n) = {for (i=1, n, if ((v = 2*prime(n) - prime(i)^2) <= 0, break;); if (bigomega(v) == 2, return (prime(i))););} \\ _Michel Marcus_, May 09 2014
%Y Cf. A001358, A241531.
%K nonn
%O 1,3
%A _Vladimir Shevelev_, Apr 25 2014
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