22410

Appears in sequences

• Open 3-dimensional ball numbers (version 2): a(n) is the number of integer points (i,j,k) contained in an open ball of diameter n, centered at (1/2,0,0).at n=35A053594
• Numbers k such that the k-th triangular number contains only digits {1,2,5}.at n=19A119102
• Triangle read by rows: T(n,k) is number of hex trees with n edges and level of first leaf (in the preorder traversal) equal to k (1 <= k <= n).at n=41A126186
• Number of ways to place 3 nonattacking nightriders on an n X n toroidal board.at n=8A196813
• Number of unlabeled rooted trees with n nodes such that the minimal outdegree of inner nodes equals 10.at n=55A244464
• a(0) = a(1) = 1; a(n) = [x^n] Product_{k=1..n-1} (1 + x^a(k))/(1 - x^a(k)).at n=50A296387
• Triangle read by rows: Take a pentagram with all diagonals drawn, as in A331906. Then T(n,k) = number of k-sided polygons in that figure for k = 3, 4, ..., n+2.at n=45A331907
• a(n) is the smallest number which can be represented as the sum of n distinct centered n-gonal numbers in exactly n ways, or -1 if no such number exists.at n=15A352975