OFFSET
0,6
COMMENTS
Imaginary part is A106202.
LINKS
Index entries for linear recurrences with constant coefficients, signature (2,-1,0,-4)
FORMULA
G.f.: x*(1-x)/(1-2*x+x^2+4*x^4).
a(n) = sum(k=0..floor((n-1)/2), C(n-k-1, k)*2^k*cos(pi*k/2) ).
MATHEMATICA
LinearRecurrence[{2, -1, 0, -4}, {0, 1, 1, 1}, 50] (* Harvey P. Dale, May 22 2020 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Apr 25 2005
STATUS
approved