A154932 - OEIS

A154932

Decimal expansion of Sum_{q in A006881} 1/(q(q-1)) over the squarefree semiprimes q.

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

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OFFSET

0,2

COMMENTS

A variant of A152447.

LINKS

Table of n, a(n) for n=0..60.

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

Adjacent sequences: A154929 A154930 A154931 * A154933 A154934 A154935

KEYWORD

cons,nonn,more

AUTHOR

R. J. Mathar, Jan 17 2009

STATUS

approved