The On-Line Encyclopedia of Integer Sequences (OEIS)

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A184121

A (4,-3) Somos-4 sequence.
(history; published version)

#10 by Charles R Greathouse IV at Thu Sep 08 08:45:55 EDT 2022

PROG

(MAGMAMagma) 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

Discussion

Thu Sep 08

08:45

OEIS Server: https://oeis.org/edit/global/2944

#9 by Michael Somos at Tue Aug 14 23:29:59 EDT 2018

STATUS

proposed

approved

#8 by G. C. Greubel at Tue Aug 14 21:09:24 EDT 2018

STATUS

editing

proposed

#7 by G. C. Greubel at Tue Aug 14 21:09:06 EDT 2018

LINKS

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

FORMULA

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

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

STATUS

approved

editing

#6 by Harvey P. Dale at Sun Apr 03 16:52:53 EDT 2016

STATUS

editing

approved

#5 by Harvey P. Dale at Sun Apr 03 16:52:49 EDT 2016

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 *)

STATUS

approved

editing

#4 by Russ Cox at Fri Mar 30 18:59:28 EDT 2012

AUTHOR

_Paul Barry (pbarry(AT)wit.ie), _, Jan 09 2011

Discussion

Fri Mar 30

18:59

OEIS Server: https://oeis.org/edit/global/287

#3 by N. J. A. Sloane at Sun Jan 09 16:37:17 EST 2011

STATUS

proposed

approved

#2 by Paul Barry at Sun Jan 09 15:51:38 EST 2011

NAME

allocated for Paul Barry

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

DATA

1, -1, -7, -31, -23, 2239, 39889, 603521, -27466831, -2445382081, -204734091383, 7545563759329, 7265319037194073, 2502938339020429439, 404477135616551491361, -932929530161758614571519

OFFSET

0,3

COMMENTS

Hankel transform of A184120.

FORMULA

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

KEYWORD

allocated

sign,easy

AUTHOR

Paul Barry (pbarry(AT)wit.ie), Jan 09 2011

STATUS

approved

proposed

#1 by Paul Barry at Sun Jan 09 15:48:20 EST 2011

NAME

allocated for Paul Barry

KEYWORD

allocated

STATUS

approved