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A142471 a(0) = a(1) = 0; thereafter a(n) = a(n-1)*a(n-2) + 2. 2
0, 0, 2, 2, 6, 14, 86, 1206, 103718, 125083910, 12973452977382, 1622770224612082123622, 21052933202100473722674133293917606, 34164073141115747076263787631563122725393126176374288934 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..19

A. V. Aho and N. J. A. Sloane, Some doubly exponential sequences, Fib. Quart., 11 (1973), 429-437.

FORMULA

a(n) ~ c^(phi^n), where c = 1.278178162398588325773605473403497130099080978627235683548955136178125... and phi = A001622 = (1+sqrt(5))/2 is the golden ratio. - Vaclav Kotesovec, May 21 2015

MATHEMATICA

a[0] = a[1] = 0; a[n_] := a[n-1] a[n-2] + 2; Table[a[n], {n, 0, 15}] (* T. D. Noe, Nov 14 2011 *)

PROG

(MAGMA) I:=[0, 0]; [n le 2 select I[n] else Self(n-1)*Self(n-2)+2: n in [1..15]]; // Vincenzo Librandi, Nov 14 2011

CROSSREFS

Cf. A007660, A000058, A143684.

Sequence in context: A014431 A201687 A259810 * A323233 A071208 A231536

Adjacent sequences:  A142468 A142469 A142470 * A142472 A142473 A142474

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, based on email from Carla J. Garner-Bennett, Nov 13 2008

STATUS

approved

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Last modified August 8 19:12 EDT 2020. Contains 336298 sequences. (Running on oeis4.)