Number of length-n 0..2 arrays with no adjacent pair x,x+1 followed at any distance by x+1,x.
A268451
Number of length-n 0..2 arrays with no adjacent pair x,x+1 followed at any distance by x+1,x.
Terms
- a(0) =3a(1) =9a(2) =25a(3) =67a(4) =176a(5) =456a(6) =1169a(7) =2971a(8) =7496a(9) =18796a(10) =46880a(11) =116386a(12) =287775a(13) =709005a(14) =1741247a(15) =4264131a(16) =10415559a(17) =25381773a(18) =61721980a(19) =149801330a(20) =362926749a(21) =877831299a(22) =2120050410a(23) =5112962906a(24) =12314976142a(25) =29625637490a(26) =71188510125
External references
- oeis: A268451