Number of compositions of n that are not a twin (x,x) but have adjacent equal parts.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =3a(5) =9a(6) =17a(7) =41a(8) =88a(9) =185a(10) =387a(11) =810a(12) =1669a(13) =3435a(14) =7039a(15) =14360a(16) =29225a(17) =59347a(18) =120228a(19) =243166a(20) =491085a(21) =990446a(22) =1995409a(23) =4016259a(24) =8076959a(25) =16231746a(26) =32599773a(27) =65437945a(28) =131293191a(29) =263316897