Gaussian binomial coefficient [ n,2 ] for q = -2.

Terms

a(0) =1a(1) =3a(2) =15a(3) =55a(4) =231a(5) =903a(6) =3655a(7) =14535a(8) =58311a(9) =232903a(10) =932295a(11) =3727815a(12) =14913991a(13) =59650503a(14) =238612935a(15) =954429895a(16) =3817763271a(17) =15270965703a(18) =61084037575a(19) =244335800775a(20) =977343902151