The number of tight 4 X n pavings.

Terms

a(0) =0a(1) =1a(2) =26a(3) =282a(4) =2072a(5) =12279a(6) =63858a(7) =305464a(8) =1382648a(9) =6029325a(10) =25628762a(11) =107026662a(12) =441439944a(13) =1804904755a(14) =7334032754a(15) =29669499492a(16) =119647095176a(17) =481400350185