Number of 0..3 arrays of length n with each element unequal to at least one neighbor, with new values introduced in 0..3 order.

A221454

Number of 0..3 arrays of length n with each element unequal to at least one neighbor, with new values introduced in 0..3 order.

Terms

    a(0) =0a(1) =1a(2) =2a(3) =7a(4) =24a(5) =88a(6) =328a(7) =1235a(8) =4668a(9) =17675a(10) =66974a(11) =253858a(12) =962352a(13) =3648397a(14) =13831870a(15) =52440191a(16) =198815196a(17) =753764564a(18) =2857736696a(19) =10834499599a(20) =41076702120a(21) =155733594211a(22) =590430871282

External references