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 A076214 Decimal expansion of C=sum(k>=0,1/2^(2^k-1)). 7
 1, 6, 3, 2, 8, 4, 3, 0, 1, 8, 0, 4, 3, 7, 8, 6, 2, 8, 7, 4, 1, 6, 1, 5, 9, 4, 7, 5, 0, 6, 1, 0, 5, 0, 4, 4, 3, 4, 0, 6, 6, 2, 2, 7, 5, 1, 8, 4, 1, 1, 0, 5, 6, 0, 8, 6, 8, 2, 4, 2, 1, 8, 0, 7, 6, 8, 6, 1, 1, 1, 2, 2, 8, 3, 8, 9, 1, 1, 0, 6, 0, 0, 1, 2, 0, 9, 7, 0, 6, 2, 6, 4, 9, 6, 7, 9, 4, 5, 3, 1, 2, 3, 5, 1, 1 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS This constant has a nice continued fraction expansion (i.e. only 1 and 2 occur). C arises when looking for a sequence b(n) such that : b(1)=0, b(n+1) is the smallest integer > b(n) such that the continued fraction for 1/2^ b(1)+1/2^b(2)+...+1/2^b(n+1) contains only 1's or 2's. Because b(n)=2^n-1 and C= sum(k>=0,1/2^b(k)). sum(1/2^(2^k - 1), k=0 to infinity) = 2*sum(1/2^(2^k), k=0 to infinity) - Harry J. Smith, May 09 2009 LINKS Harry J. Smith, Table of n, a(n) for n = 1..20000 Boris Adamczewski, The Many Faces of the Kempner Number, Journal of Integer Sequences, Vol. 16 (2013), #13.2.15. EXAMPLE 1.632843018043786287416159475061050443406622751841105608682421807686111... MATHEMATICA Take[ RealDigits[ 2*NSum[1/2^2^k, {k, 0, Infinity}, WorkingPrecision -> 120]][[1]], 105] (* Jean-François Alcover, Nov 15 2011 *) PROG (PARI) default(realprecision, 20080); x=suminf(k=0, 1/2^(2^k)); x*=2; for (n=1, 20000, d=floor(x); x=(x-d)*10; write("b076214.txt", n, " ", d)); \\ Harry J. Smith, May 09 2009 CROSSREFS Cf. A006466 (continued fraction). Sequence in context: A283443 A266263 A177707 * A011488 A021162 A114348 Adjacent sequences:  A076211 A076212 A076213 * A076215 A076216 A076217 KEYWORD cons,nonn AUTHOR Benoit Cloitre, Nov 03 2002 STATUS approved

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Last modified September 18 23:16 EDT 2021. Contains 347548 sequences. (Running on oeis4.)