18484

Appears in sequences

• Triangle read by rows: T(n,k) is number of paths from (0,0) to (3n,0) that stay in the first quadrant (but may touch the horizontal axis), consisting of steps u=(2,1),U=(1,2), or d=(1,-1) and have k pyramids (a pyramid is a sequence u^pd^p or U^pd^(2p) for some positive integer p, starting at the x-axis).at n=21A108445
• Number of paths from (0,0) to (3n,0) that stay in the first quadrant (but may touch the horizontal axis), consisting of steps u=(2,1),U=(1,2), or d=(1,-1) and having no pyramids (a pyramid is a sequence u^pd^p or U^pd^(2p) for some positive integer p, starting at the x-axis).at n=6A108449
• Triangle read by rows: T(n,k) is number of paths from (0,0) to (3n,0) that stay in the first quadrant (but may touch the horizontal axis), consisting of steps u=(2,1),U=(1,2), or d=(1,-1) and having sum of the heights of its pyramids equal to k (a pyramid is a sequence u^pd^p or U^pd^(2p) for some positive integer p, starting at the x-axis; p is the height of the pyramid).at n=36A109157
• Sum of proper divisors of Catalan number A000108(n).at n=10A152762
• Wiener indices of Fibonacci trees of order k.at n=8A165910
• Number of 2n-digit primes that are concatenation of n two-digit distinct primes p_1...p_n, 98>p_1>p_2>...>p_n>10.at n=8A168513
• Expansion of f(-x, x^2) / f(-x, -x^3)^3 in powers of x where f(, ) is Ramanujan's general theta function.at n=19A263993