%I #15 Apr 10 2024 14:16:31
%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
%E Recurrence formula corrected by _Georg Fischer_, Apr 10 2024
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