login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A122593 a(n) = -a(n-1) - a(n-3) - (a(n-1) - a(n-2))^2 + (a(n-2) - a(n-3))^2. 4

%I #12 Sep 08 2022 08:45:28

%S 1,1,1,0,0,2,-6,-54,-2184,-4532418,-20523011025492,

%T -421193795514716517978851412,

%U -177404213380075544048510970681865493733941889439557930

%N a(n) = -a(n-1) - a(n-3) - (a(n-1) - a(n-2))^2 + (a(n-2) - a(n-3))^2.

%H G. C. Greubel, <a href="/A122593/b122593.txt">Table of n, a(n) for n = 1..17</a>

%F a(n) = -a(n-1) - a(n-3) - (a(n-1) - a(n-2))^2 + (a(n-2) - a(n-3))^2, with a(1) = a(2) = a(3) = 1.

%t a[n_]:= a[n]= If[n<4, 1, -a[n-1] +a[n-3] - (a[n-1] -a[n-2])^2 + (a[n-2] -a[n-3])^2];

%t Table[a[n], {n, 15}]

%o (Magma)

%o function a(n) // a = A122593

%o if n lt 4 then return 1;

%o else return -a(n-1) +a(n-3) -(a(n-1) -a(n-2))^2 +(a(n-2) -a(n-3))^2;

%o end if; return a; end function;

%o [a(n): n in [1..15]]; // _G. C. Greubel_, Nov 29 2021

%o (Sage)

%o @CachedFunction

%o def a(n): return 1 if (n<4) else -a(n-1) +a(n-3) -(a(n-1) -a(n-2))^2 +(a(n-2) -a(n-3))^2 # a = A122593

%o [a(n) for n in (1..15)] # _G. C. Greubel_, Nov 29 2021

%Y Cf. A122590, A122591, A122592.

%K sign

%O 1,6

%A _Roger L. Bagula_, Sep 19 2006

%E Edited by _N. J. A. Sloane_, Sep 21 2006

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 15:38 EDT 2024. Contains 371254 sequences. (Running on oeis4.)