Large-number statistic from the enumeration of domino tilings of a 9-pillow of order n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =2a(7) =3a(8) =7a(9) =11a(10) =26a(11) =44a(12) =118a(13) =221a(14) =677a(15) =1721a(16) =6884a(17) =21165a(18) =95800a(19) =324693a(20) =1633462a(21) =6253408a(22) =35917622a(23) =161554715a(24) =1151376732a(25) =6387653627a(26) =54325024024a(27) =348582834189