Number of Twopins positions.

Terms

a(0) =1a(1) =2a(2) =4a(3) =7a(4) =11a(5) =16a(6) =22a(7) =30a(8) =42a(9) =61a(10) =91a(11) =137a(12) =205a(13) =303a(14) =443a(15) =644a(16) =936a(17) =1365a(18) =1999a(19) =2936a(20) =4316a(21) =6340a(22) =9300a(23) =13625a(24) =19949a(25) =29209a(26) =42785a(27) =62701a(28) =91917a(29) =134758