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 A131653 Decimal expansion of the sum of the reciprocals of squared 3-almost primes. 1
 0, 3, 8, 5, 1, 6, 1, 9, 2, 9, 8, 2, 6, 9, 4, 6, 4, 0, 9, 1, 2, 8, 3, 7, 9, 2, 2, 6, 2, 8, 0, 6, 0, 3, 9, 5, 4, 3, 8, 9, 0, 0, 1, 6, 7, 4, 7, 8, 3, 8, 1, 5, 7, 1, 9, 3, 7, 1, 9, 1, 5, 5, 8, 9, 2, 2, 3, 7, 5, 5, 3, 7, 8, 3, 4, 5, 9, 1, 6, 6, 1, 3, 9, 3, 0, 4, 7, 4, 1, 4, 7, 6, 2, 0, 4, 9, 4, 7, 1, 5, 0, 8, 4, 4, 5 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Zeta(2)=A013661 is 1 plus a sum over inverse squares of k-almost primes, k=1 to infinity, where A085548 represents k=1, A117543 represents k=2 and this constant here represents k=3. LINKS R. J. Mathar, Series of reciprocal powers of k-almost primes, arXiv:0803.0900 [math.NT]. FORMULA Equals A085548^3 / 6 + A085966 / 3 + A085548 * A085964 / 2. Equals sum_(i=1,2,...infinity) 1/A000290[A014612(i)]. EXAMPLE Equals 0.038516192982694640912837922628060395438900167478381571937... CROSSREFS Cf. A117543, A085548. Sequence in context: A016670 A021726 A221315 * A011239 A261644 A200699 Adjacent sequences:  A131650 A131651 A131652 * A131654 A131655 A131656 KEYWORD cons,nonn AUTHOR R. J. Mathar, Sep 10 2007, Mar 07 2008 STATUS approved

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