a(n) = number of (s(0), s(1), ..., s(n)) such that s(i) is a nonnegative integer and |s(i) - s(i-1)| <= 1 for i = 1,2,...,n, s(0) = 2, s(n) = 4. Also a(n) = T(n,n-2), where T is the array in A026323.

A026327

a(n) = number of (s(0), s(1), ..., s(n)) such that s(i) is a nonnegative integer and |s(i) - s(i-1)| <= 1 for i = 1,2,...,n, s(0) = 2, s(n) = 4. Also a(n) = T(n,n-2), where T is the array in A026323.

Terms

    a(0) =1a(1) =3a(2) =10a(3) =30a(4) =90a(5) =266a(6) =783a(7) =2295a(8) =6710a(9) =19580a(10) =57057a(11) =166101a(12) =483210a(13) =1405080a(14) =4084590a(15) =11872494a(16) =34508997a(17) =100313635a(18) =291646580a(19) =848102640a(20) =2466916474a(21) =7177785582a(22) =20891443950a(23) =60827142350a(24) =177167486925a(25) =516217883571

External references