A086889 - OEIS

%I #5 Mar 30 2012 18:39:21

%S 0,0,0,0,-1,1,-3,-3,-41,140,-93456,280356252,-471833669834248,

%T 40261350925439315783335171,

%U 20143180524957577201436416071451979623101429,9048277144756224572757714728840507662214586396123974675011643142128755383165

%N Real part of Propp's cubic recurrence starting with i (i^2=-1).

%C b(n)=x(n)+i*y(n) where x(n) and y(n) are integer sequences.

%F a(n)=Re(b(n)) where b(1)=b(2)=b(3)=b(4)=i and b(n)=(1+b(n-1)*b(n-2)*b(n-3))/b(n-4)

%Y Cf. A051786, A086890.

%K sign

%O 1,7

%A _Benoit Cloitre_, Sep 17 2003