A073821 - OEIS

%I #23 Nov 30 2020 08:49:12

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

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

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

%N Decimal expansion of number with continued fraction expansion 0, 2, 4, 6, ... (the even numbers).

%H Lucas A. Brown, <a href="/A073821/b073821.txt">Table of n, a(n) for n = 0..1000</a>

%F BesselI(1, 1)/BesselI(0, 1) (courtesy of the Inverse Symbolic Calculator).

%e 0.44638996589653450704768179519...

%t RealDigits[FromContinuedFraction[2Range[0,200]],10,120][[1]] (* _Harvey P. Dale_, Oct 30 2011 *)

%o (PARI) dec_exp(v)= {my(w=contfracpnqn(v)); w[1,1]/w[2,1]+0.0; }

%o dec_exp(vector(2000,i,2*(i-1)))

%Y Cf. A005843 (even numbers), A052119 (continued fraction exp. is 0, 1, 2, 3, ...), A073747 (coth(1), continued fraction exp. is odd numbers).

%K cons,nonn

%O 0,1

%A _Rick L. Shepherd_, Aug 12 2002