a(1)=1, a(2)=1, a(3)=4, a(4)=0; a(n)=12a(n-2)-16a(n-3) for n>=5.

Terms

a(0) =1a(1) =1a(2) =4a(3) =0a(4) =32a(5) =-64a(6) =384a(7) =-1280a(8) =5632a(9) =-21504a(10) =88064a(11) =-348160a(12) =1400832a(13) =-5586944a(14) =22380544a(15) =-89456640a(16) =357957632a(17) =-1431568384a(18) =5726797824a(19) =-22906142720a(20) =91626668032a(21) =-366502477824