A268021 - OEIS

%I #8 Nov 29 2022 15:30:56

%S 1,1,-1,-1,3,-5,-13,83,-1149,-94301,108447299,-10226797095997,

%T -1109068512255229713405,11342218640394605506848882609549187,

%U -12579297553175979435284002182896862386417808141640587517

%N a(1) = a(2) = 1; if n > 2 then a(n) = a(n-1)*a(n-2) - a(n-2) - a(n-1).

%F |a(n)| ~ c^(phi^n), where phi = A001622 = (1+sqrt(5))/2 is the golden ratio and c = 1.097478514051533426... . - _Vaclav Kotesovec_, Jan 26 2016

%t a[1] = 1; a[2] = 1; a[n_] := a[n] = -a[n - 1] - a[n - 2] + a[n - 1]*a[n - 2];Table[a[n], {n, 20}]

%t nxt[{a_,b_}]:={b,a*b-a-b}; NestList[nxt,{1,1},20][[All,1]] (* _Harvey P. Dale_, Nov 29 2022 *)

%K sign

%O 1,5

%A _José María Grau Ribas_, Jan 24 2016