Number of sequences of 2's and 3's of length n with curling number 3.

Terms

a(0) =0a(1) =0a(2) =2a(3) =2a(4) =4a(5) =10a(6) =20a(7) =38a(8) =82a(9) =164a(10) =328a(11) =660a(12) =1320a(13) =2640a(14) =5304a(15) =10596a(16) =21192a(17) =42424a(18) =84848a(19) =169668a(20) =339428a(21) =678856a(22) =1357712a(23) =2715548a(24) =5431096a(25) =10862192a(26) =21724746a(27) =43449380a(28) =86898760a(29) =173798220