81639

Appears in sequences

• Number of ways to write n as an ordered sum of 1s, 2s, 3s and 4s such that no 2 precedes any 1 and no 3 precedes any 1 or 2.at n=30A123569
• Number of ways to place zero or more nonadjacent 1,0 1,1 2,1 polyhexes in any orientation on a planar nXnXn triangular grid.at n=8A155217
• Numbers n such that n^2 is divisible by the sum of the distinct prime divisors of n^2 + 1.at n=31A196219