a(n) = number of (s(0), s(1), ..., s(2n)) such that s(i) is a nonnegative integer and |s(i) - s(i-1)| = 1 for i = 1,2,...,n, s(0) = 2, s(2n) = 8. Also a(n) = T(2n,n-3), where T is the array defined in A026009.

A026015

a(n) = number of (s(0), s(1), ..., s(2n)) such that s(i) is a nonnegative integer and |s(i) - s(i-1)| = 1 for i = 1,2,...,n, s(0) = 2, s(2n) = 8. Also a(n) = T(2n,n-3), where T is the array defined in A026009.

Terms

    a(0) =1a(1) =8a(2) =45a(3) =219a(4) =987a(5) =4248a(6) =17748a(7) =72675a(8) =293436a(9) =1172908a(10) =4653935a(11) =18366075a(12) =72186075a(13) =282861360a(14) =1105877880a(15) =4316224860a(16) =16825024134a(17) =65525448960a(18) =255024693434a(19) =992116674142

External references