Number of 2-sided strip polyrects with n cells.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =12a(5) =26a(6) =57a(7) =130a(8) =297a(9) =694a(10) =1622a(11) =3810a(12) =8966a(13) =21092a(14) =49732a(15) =116952a(16) =275695a(17) =647788a(18) =1525610a(19) =3581170a(20) =8424478a(21) =19757082a(22) =46425561