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A184121
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A (4,-3) Somos-4 sequence.
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2
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1, -1, -7, -31, -23, 2239, 39889, 603521, -27466831, -2445382081, -204734091383, 7545563759329, 7265319037194073, 2502938339020429439, 404477135616551491361, -932929530161758614571519
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OFFSET
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0,3
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COMMENTS
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LINKS
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FORMULA
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a(n) = (4*a(n-1)*a(n-3) - 3*a(n-2)^2)/a(n-4).
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MATHEMATICA
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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 *)
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PROG
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(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
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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