Column two-from-center of triangle A059317.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =3a(5) =13a(6) =42a(7) =146a(8) =476a(9) =1574a(10) =5122a(11) =16706a(12) =54256a(13) =176254a(14) =571954a(15) =1856245a(16) =6023681a(17) =19551939a(18) =63476314a(19) =206145075a(20) =669695819a(21) =2176401235a(22) =7075521724a(23) =23011145314a(24) =74864599954a(25) =243652588070a(26) =793264765396