Number of 2-sided strip polyiamonds with n cells.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =5a(6) =8a(7) =15a(8) =25a(9) =46a(10) =80a(11) =145a(12) =256a(13) =466a(14) =833a(15) =1513a(16) =2720a(17) =4925a(18) =8881a(19) =16063a(20) =28996a(21) =52373a(22) =94563a(23) =170620a(24) =307989a(25) =555214a(26) =1001774a(27) =1804594a(28) =3254229a(29) =5858448