Number of 2 X n 0..2 arrays with rows and antidiagonals unimodal and columns nondecreasing.

Terms

a(0) =6a(1) =36a(2) =158a(3) =548a(4) =1600a(5) =4102a(6) =9503a(7) =20299a(8) =40570a(9) =76704a(10) =138348a(11) =239630a(12) =400700a(13) =649642a(14) =1024813a(15) =1577669a(16) =2376142a(17) =3508636a(18) =5088714a(19) =7260552a(20) =10205240a(21) =14148014a(22) =19366507a(23) =26200111a(24) =35060546a(25) =46443736a(26) =60943096a(27) =79264338