%I A059918
%S A059918 1,4,40,3280,21523360,926510094425920,1716841910146256242328924544640,
%T A059918 5895092288869291585760436430706259332839105796137920554548480
%N A059918 a(n) = (3^(2^n)-1)/2.
%C A059918 Denominator of b(n) where b(n) = 1/2*(b(n-1) + 1/b(n-1)), b(0)=2. - Vladeta 
               Jovovic (vladeta(AT)eunet.rs), Aug 15 2002
%H A059918 Harry J. Smith, <a href="b059918.txt">Table of n, a(n) for n=0,...,11</
               a>
%F A059918 a(n) = a(n-1)*(3^(2^(n-1))+1) with a(0) = 1.
%F A059918 a(n) = (3^(2^n)-1)/2 = (A059723(n+1)-A059723(n))/A059723(n) = A059917(n)-1 
               = a(n-1)*A059919(n-1) = a(n-1)*(A011764(n-1)+1)
%F A059918 1 = Sum(0, inf.) 3^(2^n)/a(n+1). 1 = 3/4 + 9/40 + 81/3280 + 6561/21523360 
               + ...; with partial sums: 3/4, 39/40, 3279/3280, 21523359/21523360...[a(n)-1]/
               a(n)...==> 1. - Gary W. Adamson (qntmpkt(AT)yahoo.com), Jun 22 2003
%o A059918 (PARI) { for (n=0, 11, write("b059918.txt", n, " ", (3^(2^n) - 1)/2); 
               ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jun 30 2009]
%Y A059918 Cf. A059917.
%Y A059918 Sequence in context: A139688 A072445 A000841 this_sequence A002677 A119527 
               A074991
%Y A059918 Adjacent sequences: A059915 A059916 A059917 this_sequence A059919 A059920 
               A059921
%K A059918 nonn,frac
%O A059918 0,2
%A A059918 Henry Bottomley (se16(AT)btinternet.com), Feb 08 2001