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%I #18 Sep 08 2022 08:46:03
%S 3,9,81,21,1359,2727,21837,21843,349515,699045,5592393,2796201,
%T 89478471,178956963,1431655749,1431655761,22906492227,45812984481,
%U 366503875905,22906492245,5864062014783,11728124029599,93824992236861,93824992236879,1501199875790139
%N Numerator of sum(i=1..n, 3*i/4^i )
%C The limit as n goes to infinity is 4/3.
%D Calvin C. Clawson, The Beauty and Magic of Numbers. New York: Plenum Press (1996): 96.
%H Vincenzo Librandi, <a href="/A215712/b215712.txt">Table of n, a(n) for n = 1..1000</a>
%e 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.
%t Table[Numerator[Sum[3i/4^i, {i, n}]], {n, 40}]
%o (Magma) [Numerator(&+[3*i/4^i: i in [1..n]]): n in [1..25]]; // _Bruno Berselli_, Sep 03 2012
%Y Cf. A215713 for the denominators.
%Y A036295/A036296 is the same with i/2^i instead of 3i/4^i.
%Y Cf. A122553.
%K nonn,easy,frac
%O 1,1
%A _Alonso del Arte_, Aug 21 2012
%E a(17) corrected by _Vincenzo Librandi_, Sep 04 2012
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