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 A073415 Denominator of the n-th convergent to Sum_{k>=0} 1/2^(2^k). 3
 1, 1, 5, 11, 49, 207, 1291, 5371, 12033, 53503, 333051, 719605, 3211471, 19988431, 83165195, 352649211, 788463617, 3506503679, 21827485691, 47161475061, 210473385935, 889055018801, 5544803498741, 23068269013765, 51681341526271 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Robert Israel, Table of n, a(n) for n = 1..1650 FORMULA a(n) = a(n-1) A007400(n) + a(n-2). - Robert Israel, Jun 14 2016 MAPLE a007400:= proc(n) option remember; local n8, n16;     n8:= n mod 8;     if n8 = 0 or n8 = 3 then return 2     elif n8 = 4 or n8 = 7 then return 4     elif n8 = 1 then return procname((n+1)/2)     elif n8 = 2 then return procname((n+2)/2)     fi;     n16:= n mod 16;     if n16 = 5 or n16 = 14 then return 4     elif n16 = 6 or n16 = 13 then return 6     fi end proc: a007400(0):= 0: a007400(1):= 1: a007400(2):= 4: A[1]:= 1: A[2]:= 1: for n from 3 to 100 do   A[n]:= A[n-1]*a007400(n-1)+A[n-2]; od: seq(A[n], n=1..100); # Robert Israel, Jun 14 2016 PROG (PARI) a(n)=component(component(contfracpnqn(contfrac(sum(k=0, 20, 1/2^(2^k)), n)), 1), 2) CROSSREFS Cf. A007400, A007404, A073414. Sequence in context: A149518 A149519 A149520 * A176832 A289284 A149521 Adjacent sequences:  A073412 A073413 A073414 * A073416 A073417 A073418 KEYWORD easy,frac,nonn AUTHOR Benoit Cloitre, Aug 23 2002 STATUS approved

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Last modified March 31 19:37 EDT 2020. Contains 333151 sequences. (Running on oeis4.)