Number of compositions of n with exactly 2 adjacent equal parts (2 pairs or 1 triple.).

Terms

a(0) =1a(1) =0a(2) =2a(3) =8a(4) =10a(5) =22a(6) =58a(7) =112a(8) =219a(9) =466a(10) =920a(11) =1787a(12) =3600a(13) =7025a(14) =13532a(15) =26315a(16) =50625a(17) =96775a(18) =185000a(19) =351714a(20) =665942a(21) =1258649a(22) =2371219a(23) =4454004a(24) =8348735a(25) =15612146a(26) =29128863a(27) =54245790a(28) =100828939a(29) =187074952