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A219164 Recurrence equation a(n+1) = a(n)^4 - 4*a(n)^2 + 2 with a(0) = 5. 3
5, 527, 77132286527, 35395236908668169265765137996816180039862527 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Bisection of A003487.

The next term -- a(4) -- has 175 digits. - Harvey P. Dale, Jun 09 2017

LINKS

Table of n, a(n) for n=0..3.

FORMULA

Let alpha = 1/2*(5 + sqrt(21)). Then a(n) = (alpha)^(4^n) + (1/alpha)^(4^n).

a(n) = A003487(2*n) = A003501(4^n).

Product {n = 0..inf} ((1 + 2/a(n))/(1 - 2/a(n)^2)) = sqrt(7/3).

MATHEMATICA

NestList[#^4-4#^2+2&, 5, 5] (* Harvey P. Dale, Jun 09 2017 *)

CROSSREFS

Cf. A001999, A003487, A003501, A219162, A219163, A219165.

Sequence in context: A283632 A270963 A110721 * A067446 A249895 A241325

Adjacent sequences:  A219161 A219162 A219163 * A219165 A219166 A219167

KEYWORD

nonn,easy

AUTHOR

Peter Bala, Nov 13 2012

STATUS

approved

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Last modified September 25 07:19 EDT 2022. Contains 356959 sequences. (Running on oeis4.)