a(n) = round(3F2([1, 3/2, 1 - n], [2, 2], -4)).

Terms

a(0) =0a(1) =1a(2) =3a(3) =7a(4) =24a(5) =87a(6) =332a(7) =1320a(8) =5407a(9) =22672a(10) =96844a(11) =419910a(12) =1843386a(13) =8176962a(14) =36594388a(15) =165026353a(16) =749170529a(17) =3420949803a(18) =15702232962a(19) =72407225094a(20) =335276107549