Number of compositions of n such that no two adjacent parts are equal, allowing 0.

Terms

a(0) =2a(1) =4a(2) =8a(3) =24a(4) =60a(5) =152a(6) =400a(7) =1032a(8) =2656a(9) =6876a(10) =17776a(11) =45912a(12) =118664a(13) =306680a(14) =792480a(15) =2047984a(16) =5292564a(17) =13677160a(18) =35345112a(19) =91340568a(20) =236046088a(21) =610000528a(22) =1576390448a(23) =4073776744a(24) =10527631456a(25) =27205966108a(26) =70306845872a(27) =181690021616a(28) =469531293752