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A303110
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Number of partitions of n into two parts (p,q), with p < q, such that neither p+q nor |q-p| is semiprime.
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2
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0, 0, 1, 0, 2, 0, 3, 1, 0, 0, 4, 2, 5, 0, 0, 3, 6, 4, 7, 5, 0, 0, 8, 6, 0, 0, 9, 7, 10, 8, 11, 9, 0, 0, 0, 10, 12, 0, 0, 11, 13, 12, 14, 13, 15, 0, 16, 14, 0, 15, 0, 16, 17, 17, 0, 18, 0, 0, 18, 19, 19, 0, 20, 20, 0, 21, 21, 22, 0, 23, 22, 24, 23, 0, 24, 25
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OFFSET
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1,5
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LINKS
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FORMULA
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a(n) = Sum_{i=1..floor((n-1)/2) (1-[Omega(n-2i) = 2]) * (1-[Omega(n) = 2]), where [] is the Iverson bracket and Omega = A001222.
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MATHEMATICA
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Table[Sum[(1 - KroneckerDelta[PrimeOmega[n - 2 i], 2]) (1 - KroneckerDelta[PrimeOmega[n], 2]), {i, Floor[(n - 1)/2]}], {n, 100}]
Table[Count[IntegerPartitions[n, {2}], _?(PrimeOmega[Total[#]]!=2&&PrimeOmega[ Abs[#[[1]]-#[[2]]]]!=2&)], {n, 80}] (* Harvey P. Dale, Jan 03 2019 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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