682341000

Appears in sequences

• a(n) = number of (s(0), s(1), ..., s(2*n-1)) such that s(i) is a nonnegative integer and |s(i) - s(i-1)| = 1 for i = 1,2,...,n, s(0) = 2, s(2*n-1) = 5. Also a(n) = T(2*n-1,n-2), where T is the array defined in A026009.at n=15A026017
• Level of the first leaf (in preorder traversal) of a binary tree, summed over all binary trees with n edges. A binary tree is a rooted tree in which each vertex has at most two children and each child of a vertex is designated as its left or right child.at n=15A120989
• a(n) = 10/(n + 1) * Catalan(3*n).at n=6A387249