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The OEIS is supported by the many generous donors to the OEIS Foundation.
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with(numtheory); A014612:=n->`if`(bigomega(n)=3, n, NULL); seq(A014612(n), n=1..250) ; # Wesley Ivan Hurt, Feb 05 2014
(* Alternative: *)
(* Alternative: *)
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Sum 1/a(n)^2 = A131653. - R. J. Mathar, Sep 15 2026
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proposed
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Edmund Landau, Handbuch der Lehre von der Verteilung der Primzahlen, <a href="httphttps://name.umdl.umich.edu/ABV2766.0001.001">vol. 1</a> and <a href="httphttps://name.umdl.umich.edu/ABV2766.0002.001">vol. 2</a>, Leipzig, Berlin, B. G. Teubner, 1909. See Vol. 1, p. 211.
Xianmeng Meng, <a href="httphttps://dx.doi.org/10.1016/j.jnt.2005.04.013">On sums of three integers with a fixed number of prime factors</a>, Journal of Number Theory, Vol. 114 (2005), pp. 37-65.
Chai Wah Wu, <a href="https://math.colgate.edu/~integers/z95/z95.pdf">Algorithms for Complementary Sequences</a>, Integers (2025) Vol. 25, Art. No. A95. See p. 24.
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Eric Weisstein's World of Mathematics, <a href="httphttps://mathworld.wolfram.com/AlmostPrime.html">Almost Prime</a>
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