A211878 - OEIS

%I #16 Feb 20 2014 08:54:53

%S 1,3,2,9,0,5,9,1,0,8,7,4,9,5,5,9,5,6,4,6,0,9,9,1,6,8,2,6,7,9,2,4,3,6,

%T 2,5,1,9,4,9,7,7,6,5,9,3,8,8,4,1,8,2,8,7,8,7,3,4,2,2,9,8,5,0,2,7,3,0,

%U 4,0,8,5,4,4,9,2,0,4,4,7,6,3,4,8,0,3,8,3,8,2,7,7,9,7,8,1,9,1,2,2,9,6,8,0,1,9,3,2,3,8,6,6

%N Decimal expansion of positive constant C such that 1 = Sum_{k>=1} 1/C^(2^k).

%e C = 1.3290591087495595646...

%p Digits:= 120:

%p s:= convert(fsolve(sum(1/C^(2^k), k=1..infinity)=1, C=1)/10, string):

%p seq(parse(s[n+1]), n=1..112);

%t digits = 112; f[x_?NumericQ] := NSum[1/x^(2^k), {k, 1, Infinity}, WorkingPrecision -> digits]; x /. FindRoot[f[x] == 1, {x, 3/2, 1, 2}, WorkingPrecision -> digits] // RealDigits[#, 10, digits]& // First (* _Jean-François Alcover_, Feb 20 2014 *)

%K cons,nonn

%O 1,2

%A _Jimmy Zotos_ and _Balarka Sen_, Feb 13 2013

%E More terms from _Alois P. Heinz_, Feb 13 2013