21108

Appears in sequences

• Expansion of 1/(1-2*x^2-3*x^3).at n=17A002447
• One fifth of the sum of the first n primes, when an integer.at n=33A112271
• Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0) and consisting of n steps taken from {(-1, -1), (-1, 1), (-1, 0), (0, -1), (0, 1), (1, -1), (1, 0)}.at n=7A151305
• The number of phi-partitions of n.at n=54A283528
• Triangle read by rows: Take a hexagon with all diagonals drawn, as in A331931. Then T(n,k) = number of k-sided polygons in that figure for k = 3, 4, ..., n+4.at n=25A331932
• The number of edges on a 2 by 1 ellipse formed by the straight line segments mutually connecting all points formed by dividing the ellipse into 2n equal angle sectors from its origin.at n=11A341764