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Least positive integer that can be represented as the sum of exactly two semiprimes in exactly n ways.
4

%I #15 Oct 30 2018 10:31:02

%S 1,8,18,30,43,48,60,72,91,108,132,155,120,144,192,168,216,236,227,180,

%T 320,340,240,252,348,300,324,336,488,484,456,396,614,360,524,548,706,

%U 468,536,656,628,420,624,576,612,588,540,600,648,768,732,800,832,660

%N Least positive integer that can be represented as the sum of exactly two semiprimes in exactly n ways.

%C A072931(a(n)) = n and A072931(m) < n for m < a(n). [From _Reinhard Zumkeller_, Jan 21 2010]

%H Reinhard Zumkeller and Zak Seidov, <a href="/A100592/b100592.txt">Table of n, a(n) for n = 0..1000</a> (Terms 0-250 from Reinhard Zumkeller)

%F a(n) = min{i such that i = A001358(j) + A001358(k) in n ways}.

%e a(0) = 1 because 1 is the smallest positive integer that cannot be represented as sum of two semiprimes (since 4 is the smallest semiprime). a(1) = 8 because 8 is the smallest such sum of two semiprimes: 4 + 4. Similarly a(2) = 18 because 18 = 14 + 4 = 9 + 9 where {4,9,14} are semiprimes and there is no third such sum for 18.

%Y Cf. A001358, A076768, A100570, A072966.

%K easy,nonn

%O 0,2

%A _Jonathan Vos Post_, Nov 30 2004