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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; 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 (vladeta(AT)eunet.rs), 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(0, inf.) 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)...==> 1. - Gary W. Adamson (qntmpkt(AT)yahoo.com), Jun 22 2003

PROG

(PARI) { for (n=0, 11, write("b059918.txt", n, " ", (3^(2^n) - 1)/2); ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jun 30 2009]

CROSSREFS

Cf. A059917.

Sequence in context: A197356 A072445 A000841 * A002677 A119527 A074991

Adjacent sequences:  A059915 A059916 A059917 * A059919 A059920 A059921

KEYWORD

nonn,frac

AUTHOR

Henry Bottomley (se16(AT)btinternet.com), Feb 08 2001

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Last modified February 17 00:09 EST 2012. Contains 205978 sequences.