A086889 Real part of Propp's cubic recurrence starting with i (i^2=-1).

0, 0, 0, 0, -1, 1, -3, -3, -41, 140, -93456, 280356252, -471833669834248, 40261350925439315783335171, 20143180524957577201436416071451979623101429, 9048277144756224572757714728840507662214586396123974675011643142128755383165

Offset: 1

Author

Benoit Cloitre, Sep 17 2003

Keywords

• sign

Comments

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

Crossrefs

Cf. A051786, A086890.

Formula

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)