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A184121 A (4,-3) Somos-4 sequence. 2
1, -1, -7, -31, -23, 2239, 39889, 603521, -27466831, -2445382081, -204734091383, 7545563759329, 7265319037194073, 2502938339020429439, 404477135616551491361, -932929530161758614571519 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Hankel transform of A184120.

LINKS

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

FORMULA

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

MATHEMATICA

RecurrenceTable[{a[0]==1, a[1]==-1, a[2]==-7, a[3]==-31, a[n]==(4a[n-1] a[n-3]- 3a[n-2]^2)/a[n-4]}, a, {n, 20}] (* Harvey P. Dale, Apr 03 2016 *)

PROG

(MAGMA) I:=[-23, 2239, 39889, 603521]; [1, -1, -7, -31] cat [n le 4 select I[n] else (4*Self(n-1)*Self(n-3) - 3*Self(n-2)^2 )/Self(n-4): n in [1..30]]; // G. C. Greubel, Aug 14 2018

CROSSREFS

Sequence in context: A221402 A065916 A122654 * A167768 A103630 A205711

Adjacent sequences:  A184118 A184119 A184120 * A184122 A184123 A184124

KEYWORD

sign,easy

AUTHOR

Paul Barry, Jan 09 2011

STATUS

approved

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Last modified January 24 13:11 EST 2022. Contains 350538 sequences. (Running on oeis4.)