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%I #13 Nov 18 2017 17:20:44
%S 4,15,55,119,253,403,697,893,1357,1943,2263,3071,3977,4429,5123,6731,
%T 8083,9089,10519,11857,13067,15089,16351,18779,22019,23533,24823,
%U 27499,29321,31301,35941,40217,42881,46009,51703,53303,57619,61777,64963,69373,75001
%N a(n) = prime(n) * prime(2*n-1).
%C A020639(a(n)) = A000040(n); A006530(a(n)) = A031368(n);
%C a(n) is central term of row 2n-1 of semiprimes triangle (A087112).
%H Reinhard Zumkeller, <a href="/A219603/b219603.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = A000040(n) * A031368(n).
%o (Haskell)
%o a219603 n = a000040 n * a031368 n
%o (PARI) a(n)=prime(n) * prime(2*n-1) \\ _Charles R Greathouse IV_, Feb 07 2017
%Y Subsequence of A001358.
%Y Cf. A006094.
%K nonn
%O 1,1
%A _Reinhard Zumkeller_, Nov 25 2012
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