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A226982
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a(n) = ceiling(n/2) - primepi(n).
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0
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1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 11, 11, 11, 11, 12, 12, 13, 13, 13, 13, 13, 13, 14, 14, 15, 15, 15
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listen;
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internal format)
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OFFSET
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1,15
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COMMENTS
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The number of partitions of 2n into exactly two parts such that the smaller part is an odd composite integer, n > 1.
Sequence decreases by 1 when n is an even prime and increases by 1 when n is an odd composite. - Wesley Ivan Hurt, Dec 27 2013
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LINKS
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FORMULA
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EXAMPLE
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a(18) =2. 2*18=38 has two partitions into exactly two odd parts with smallest part composite: (27,9) and (21,15). - Wesley Ivan Hurt, Dec 27 2013
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MAPLE
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seq(ceil(n/2)-numtheory[pi](n), n=1..100);
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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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