Number of partitions of the graph G_n (defined below) into "strokes".

Terms

a(0) =2a(1) =6a(2) =12a(3) =22a(4) =40a(5) =74a(6) =140a(7) =270a(8) =528a(9) =1042a(10) =2068a(11) =4118a(12) =8216a(13) =16410a(14) =32796a(15) =65566a(16) =131104a(17) =262178a(18) =524324a(19) =1048614a(20) =2097192a(21) =4194346a(22) =8388652a(23) =16777262a(24) =33554480a(25) =67108914a(26) =134217780a(27) =268435510a(28) =536870968a(29) =1073741882