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%I #25 Aug 02 2020 22:56:28
%S 4,9,15,21,35,33,39,65,51,57,95,69,115,161,87,93,155,217,111,185,123,
%T 129,215,141,235,329,159,265,371,177,183,305,427,201,335,213,219,365,
%U 511,237,395,249,415,581,267,445,623,1501,291,485,303,309,515,321,327
%N Write 2*n = p+q (p,q prime), p*q minimal; then a(n) = p*q.
%C Least semiprime whose sum of prime factors equals 2*n.
%C Assuming Goldbach's conjecture, a(n) exists for all n >= 2. - _David James Sycamore_, Jan 08 2019
%H Reinhard Zumkeller, <a href="/A073046/b073046.txt">Table of n, a(n) for n = 2..10000</a>
%F For all n except 3, a(n) = A288814(2*n). - _David James Sycamore_, Jan 08 2019
%e n=13: 2n=26; 26 = 23 + 3 = 19 + 7 = 13 + 13; 23*3 = minimal => p*q = 23*3 = 69.
%t Array[Block[{p = 2, q}, While[! PrimeQ@ Set[q, 2 # - p], p = NextPrime[p]]; p q] &, 55, 2] (* _Michael De Vlieger_, Aug 02 2020 *)
%o (Haskell)
%o a073046 n = head $ dropWhile (== 0) $
%o zipWith (*) prims $ map (a061397 . (2*n -)) prims
%o where prims = takeWhile (<= n) a000040_list
%o -- _Reinhard Zumkeller_, Aug 28 2011
%Y Cf. A000040, A061397.
%Y Cf. A102084, A193315, A288814.
%K nonn
%O 2,1
%A _Werner D. Sand_, Aug 31 2002
%E Corrected by _Ray Chandler_, Jun 11 2005
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