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 A215712 Numerator of sum(i=1..n, 3*i/4^i ) 2
 3, 9, 81, 21, 1359, 2727, 21837, 21843, 349515, 699045, 5592393, 2796201, 89478471, 178956963, 1431655749, 1431655761, 22906492227, 45812984481, 366503875905, 22906492245, 5864062014783, 11728124029599, 93824992236861, 93824992236879, 1501199875790139 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The limit as n goes to infinity is 4/3. REFERENCES Calvin C. Clawson, The Beauty and Magic of Numbers. New York: Plenum Press (1996): 96. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 EXAMPLE a(4) = 21 because 3/4 + 6/16 + 9/64 + 12/256 = 3/4 + 3/8 + 9/64 + 3/64 = 48/64 + 24/64 + 9/64 + 3/64 = 84/64 = 21/16. MATHEMATICA Table[Numerator[Sum[3i/4^i, {i, n}]], {n, 40}] PROG (Magma) [Numerator(&+[3*i/4^i: i in [1..n]]): n in [1..25]]; // Bruno Berselli, Sep 03 2012 CROSSREFS Cf. A215713 for the denominators. A036295/A036296 is the same with i/2^i instead of 3i/4^i. Cf. A122553. Sequence in context: A032330 A018604 A301535 * A000218 A139731 A259986 Adjacent sequences: A215709 A215710 A215711 * A215713 A215714 A215715 KEYWORD nonn,easy,frac AUTHOR Alonso del Arte, Aug 21 2012 EXTENSIONS a(17) corrected by Vincenzo Librandi, Sep 04 2012 STATUS approved

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Last modified March 31 17:18 EDT 2023. Contains 361668 sequences. (Running on oeis4.)