A072882 - OEIS

A072882

A nonlinear recurrence of order 3: a(1)=a(2)=a(3)=1; a(n)=(a(n-1)+a(n-2))^2/a(n-3).

1, 1, 1, 4, 25, 841, 187489, 1418727556, 2393959458891025, 30567386265691995561839449, 658593751358960570203157512237008273218521, 181183406309644143341701434158730639946454023369335051404405528107396

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OFFSET

1,4

COMMENTS

All terms are perfect squares.

LINKS

Seiichi Manyama, Table of n, a(n) for n = 1..17

FORMULA

a(n) ~ 1/9 * c^(((1+sqrt(5))/2)^n), where c = 1.6403763522562240514693138664331346215549... . - Vaclav Kotesovec, May 06 2015

a(n) = A064098(n)^2. - Seiichi Manyama, Aug 18 2016

From Seiichi Manyama, Aug 26 2016: (Start)

a(n) = 9*a(n-1)*a(n-2) - 2*a(n-1) - 2*a(n-2) - a(n-3).

a(n)*a(n-1)*a(n-2) = ((a(n) + a(n-1) + a(n-2))/3)^2. (End)

MATHEMATICA

RecurrenceTable[{a[1]==1, a[2]==1, a[3]==1, a[n]==(a[n-1]+a[n-2])^2/a[n-3]}, a, {n, 1, 10}] (* Vaclav Kotesovec, May 06 2015 *)

CROSSREFS

Cf. A064098, A276095, A276097.

Sequence in context: A004019 A302092 A277110 * A014253 A132553 A305679

Adjacent sequences: A072879 A072880 A072881 * A072883 A072884 A072885

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Jul 28 2002

STATUS

approved