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A072931
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Number of ways to write n as a sum of 2 semiprimes.
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7
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0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 2, 2, 2, 1, 0, 1, 2, 2, 1, 1, 2, 2, 3, 3, 2, 0, 1, 3, 3, 2, 1, 3, 3, 2, 3, 4, 4, 2, 1, 4, 5, 3, 3, 1, 3, 3, 2, 5, 3, 2, 2, 5, 6, 6, 1, 3, 5, 3, 4, 4, 5, 3, 3, 6, 7, 5, 3, 3, 4, 4, 4, 5, 5, 3, 2, 7, 7, 2, 4, 4, 5, 4, 6, 8, 6, 3, 3, 8, 7, 7, 4, 6, 8, 6, 5, 7, 7, 2
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,18
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COMMENTS
| Sequence is probably >0 for n> 33.
The graph of this sequence is compelling evidence that 33 is the last term of sequence A072966. - T. D. Noe, Apr 10 2007
A072931(A100592(n))=n and A072931(m)<n for m < A100592(n); A171963(n)=a(A001358(n)). [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jan 21 2010]
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..10000
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PROG
| (PARI) a(n)=sum(i=1, n, sum(j=1, i, if(abs(bigomega(i)-2)+abs(bigomega(j)-2)+abs(n-i-j), 0, 1)))
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CROSSREFS
| Cf. A001358, A072966.
Cf. A101048. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jan 21 2010]
Sequence in context: A124747 A039981 A006140 * A112211 A112215 A176389
Adjacent sequences: A072928 A072929 A072930 * A072932 A072933 A072934
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 13 2002
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