Number of 0..3 arrays of length n with each element differing from at least one neighbor by 1 or less, starting with 0.

A221678

Number of 0..3 arrays of length n with each element differing from at least one neighbor by 1 or less, starting with 0.

Terms

    a(0) =0a(1) =2a(2) =5a(3) =20a(4) =68a(5) =241a(6) =844a(7) =2966a(8) =10413a(9) =36568a(10) =128408a(11) =450913a(12) =1583400a(13) =5560186a(14) =19524853a(15) =68562444a(16) =240760252a(17) =845440977a(18) =2968805844a(19) =10425101678a(20) =36608235997a(21) =128551546480a(22) =451414815600

External references