OFFSET
1,2
FORMULA
Apparently, a(n+1) = (n+1)2^n - (n+2)/4 * (I^n + (-I)^n).
Empirical g.f.: x^2*(x+2)*(x^2-2*x+2) / ((2*x-1)^2*(x^2+1)^2). - Colin Barker, Jul 16 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Ralf Stephan, Oct 24 2004
STATUS
approved