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A184019 A (9,-5) Somos-4 sequence 2
1, 2, 13, 97, 901, 29186, 1647721, 93837697, 12290566873, 4736355079682, 1969233690270421, 1126004701770879841, 2327721451902521875261, 7371705459667139440634882, 24178816113044965430498802193, 208545961878958994572139555513857, 4688266673793881234527843412398379761 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Hankel transform of A184018.

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..75

FORMULA

a(n) = (9*a(n-1)*a(n-3) - 5*a(n-2)^2)/a(n-4).

MATHEMATICA

a[n_] := a[n] = (9 a[n - 1] a[n - 3] - 5 a[n - 2]^2)/a[n - 4]; a[0] = 1; a[1] = 2; a[2] = 13; a[3] = 97; Array[a, 17, 0]

RecurrenceTable[{a[0]==1, a[1]==2, a[2]==13, a[3]==97, a[n]==(9a[n-1]a[n-3]- 5a[n-2]^2)/a[n-4]}, a[n], {n, 20}] (* Harvey P. Dale, Sep 06 2011 *)

PROG

(MAGMA) I:=[901, 29186, 1647721, 93837697]; [1, 2, 13, 97] cat [n le 4 select I[n] else (9*Self(n-1)*Self(n-3) - 5*Self(n-2)^2)/Self(n-4): n in [1..30]]; // G. C. Greubel, Aug 14 2018

CROSSREFS

Sequence in context: A118352 A320360 A074614 * A300633 A064325 A123619

Adjacent sequences:  A184016 A184017 A184018 * A184020 A184021 A184022

KEYWORD

nonn

AUTHOR

Paul Barry, Jan 08 2011

STATUS

approved

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Last modified February 16 14:47 EST 2019. Contains 320163 sequences. (Running on oeis4.)