Number of length-5 0..n arrays with no adjacent pair x,x+1 followed at any distance by x+1,x.

Terms

a(0) =16a(1) =176a(2) =852a(3) =2776a(4) =7160a(5) =15816a(6) =31276a(7) =56912a(8) =97056a(9) =157120a(10) =243716a(11) =364776a(12) =529672a(13) =749336a(14) =1036380a(15) =1405216a(16) =1872176a(17) =2455632a(18) =3176116a(19) =4056440a(20) =5121816a(21) =6399976a(22) =7921292a(23) =9718896a(24) =11828800a(25) =14290016a(26) =17144676a(27) =20438152a(28) =24219176