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A072931 Number of ways to write n as a sum of 2 semiprimes. 7
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; text; internal format)
OFFSET

1,18

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, Jan 21 2010]

LINKS

T. D. Noe, Table of n, a(n) for n=1..10000

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)))

CROSSREFS

Cf. A001358, A072966.

Cf. A101048. [From Reinhard Zumkeller, Jan 21 2010]

Sequence in context: A124747 A039981 A006140 * A112211 A112215 A176389

Adjacent sequences:  A072928 A072929 A072930 * A072932 A072933 A072934

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Aug 13 2002

STATUS

approved

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Last modified May 18 21:01 EDT 2013. Contains 225428 sequences.