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A184121 A (4,-3) Somos-4 sequence. 2

%I #10 Sep 08 2022 08:45:55

%S 1,-1,-7,-31,-23,2239,39889,603521,-27466831,-2445382081,

%T -204734091383,7545563759329,7265319037194073,2502938339020429439,

%U 404477135616551491361,-932929530161758614571519

%N A (4,-3) Somos-4 sequence.

%C Hankel transform of A184120.

%H G. C. Greubel, <a href="/A184121/b184121.txt">Table of n, a(n) for n = 0..75</a>

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

%t 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 *)

%o (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

%K sign,easy

%O 0,3

%A _Paul Barry_, Jan 09 2011

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Last modified March 3 17:49 EST 2024. Contains 370512 sequences. (Running on oeis4.)