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A059918 a(n) = (3^(2^n)-1)/2. 4
1, 4, 40, 3280, 21523360, 926510094425920, 1716841910146256242328924544640, 5895092288869291585760436430706259332839105796137920554548480 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Denominator of b(n) where b(n) = 1/2*(b(n-1) + 1/b(n-1)), b(0)=2. - Vladeta Jovovic, Aug 15 2002

LINKS

Harry J. Smith, Table of n, a(n) for n = 0..11

FORMULA

a(n) = a(n-1)*(3^(2^(n-1))+1) with a(0) = 1.

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)

1 = sum(n>=0, 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), ... . - Gary W. Adamson, Jun 22 2003

A136308(n) = A007089(a(n)). - Jason Kimberley, Dec 19 2012

PROG

(PARI) { for (n=0, 11, write("b059918.txt", n, " ", (3^(2^n) - 1)/2); ) } \\ Harry J. Smith, Jun 30 2009

CROSSREFS

Cf. A059917.

Sequence in context: A303124 A072445 A000841 * A296101 A002677 A119527

Adjacent sequences:  A059915 A059916 A059917 * A059919 A059920 A059921

KEYWORD

nonn,easy

AUTHOR

Henry Bottomley, Feb 08 2001

STATUS

approved

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Last modified December 13 23:26 EST 2018. Contains 318087 sequences. (Running on oeis4.)