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A154932
Decimal expansion of Sum_{q in A006881} 1/(q(q-1)) over the squarefree semiprimes q.
2
0, 7, 1, 6, 0, 6, 0, 1, 5, 3, 6, 4, 0, 6, 2, 9, 5, 0, 6, 8, 9, 0, 1, 4, 9, 0, 5, 2, 3, 3, 2, 7, 8, 5, 7, 0, 0, 3, 2, 9, 7, 7, 5, 7, 7, 4, 9, 6, 7, 6, 4, 7, 6, 6, 9, 9, 6, 8, 8, 1, 5
OFFSET
0,2
COMMENTS
A variant of A152447.
LINKS
R. J. Mathar, Series of reciprocal powers of k-almost primes, arXiv:0803.0900 [math.NT], 2008-2009; see Table 9.
FORMULA
Equals Sum_{j>=1} 1/(A006881(j)*(A006881(j)-1)) = A152447 - Sum_{p in A000040} 1/(p^2*(p^2-1)) = A152447 + A085548 - Sum_{p in A000040} 1/(p^2-1).
EXAMPLE
Equals 0.071606015364062950... = 1/(6*5) + 1/(10*9) + 1/(14*13) + 1/(15*14) + ...
CROSSREFS
Sequence in context: A089204 A107786 A246949 * A026497 A010146 A229342
KEYWORD
cons,nonn,more
AUTHOR
R. J. Mathar, Jan 17 2009
STATUS
approved