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%I #23 Sep 08 2022 08:45:28
%S 1,1,1,0,2,4,4,2,6,18,144,15882,247684656,61339821614663208,
%T 3762573685332838515711641628032454,
%U 14156960737559137644661747812427568488753428461913274274176986277422
%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="/A122592/b122592.txt">Table of n, a(n) for n = 1..19</a>
%F a(n) = a(n-1) - 2*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 (* First program *)
%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,20}]
%t (* Second program *)
%t RecurrenceTable[{a[1]==a[2]==a[3]==1, a[n]==-a[n-1]+a[n-3]+(a[n-2]-a[n-1])^2+(a[n-2]-a[n-3])^2}, a, {n,20}] (* _Harvey P. Dale_, Dec 18 2012 *)
%o (Magma)
%o function a(n) // a = A122592
%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..18]]; // _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 = A122592
%o [a(n) for n in (1..18)] # _G. C. Greubel_, Nov 29 2021
%Y Cf. A122590, A122591, A122593.
%K nonn
%O 1,5
%A _Roger L. Bagula_, Sep 19 2006
%E Edited by _N. J. A. Sloane_, Sep 21 2006
%E Definition corrected by _Harvey P. Dale_, Dec 18 2012
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