Number of Twopins positions.

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =9a(5) =14a(6) =22a(7) =36a(8) =57a(9) =90a(10) =139a(11) =214a(12) =329a(13) =506a(14) =780a(15) =1200a(16) =1845a(17) =2830a(18) =4337a(19) =6642a(20) =10170a(21) =15572a(22) =23838a(23) =36486a(24) =55828a(25) =85408a(26) =130641a(27) =199814a(28) =305599a(29) =467366