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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

Table of n, a(n) for n=0..100.

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: A094876 A144159 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 February 23 13:38 EST 2018. Contains 299581 sequences. (Running on oeis4.)