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 A285797 Number of ways to write n as an ordered sum of two numbers that are the product of an odd number of distinct primes. 2
 0, 0, 0, 0, 1, 2, 1, 2, 2, 2, 3, 0, 2, 2, 3, 2, 4, 0, 4, 2, 4, 2, 5, 0, 6, 2, 5, 0, 4, 0, 6, 2, 6, 4, 7, 2, 8, 2, 3, 2, 6, 2, 8, 4, 8, 4, 7, 4, 10, 6, 8, 0, 6, 4, 10, 4, 6, 0, 7, 4, 13, 6, 5, 2, 10, 2, 12, 2, 6, 4, 10, 6, 16, 10, 9, 4, 10, 6, 14, 4, 10, 6, 9, 10, 17, 8, 9, 2, 8, 10, 18, 6, 8, 2, 9, 6, 16, 6, 6, 4, 14 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,6 COMMENTS Conjecture: a(n) > 0 for all n > 57. LINKS FORMULA G.f.: (Sum_{k>=1} x^A030059(k))^2. EXAMPLE a(10) = 3 because we have [7, 3], [5, 5] and [3, 7]. MATHEMATICA nmax = 100; CoefficientList[Series[(Sum[Boole[MoebiusMu[k] == -1] x^k, {k, 1, nmax}])^2, {x, 0, nmax}], x] CROSSREFS Cf. A005117, A030059, A098235, A285796. Sequence in context: A144159 A318662 A073610 * A131840 A179752 A085693 Adjacent sequences:  A285794 A285795 A285796 * A285798 A285799 A285800 KEYWORD nonn AUTHOR Ilya Gutkovskiy, Apr 26 2017 STATUS approved

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Last modified June 14 01:29 EDT 2021. Contains 345016 sequences. (Running on oeis4.)