111924

Appears in sequences

• First occurrence of just n semiprimes occurs between the a(n)-th prime and the next prime.at n=33A103669
• a(n) = a(n-1) + A000045(n)*a(n-2), a(1) = 1, a(2) = 1.at n=9A135686
• Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, up, up.at n=4A177578
• Number of n X n symmetric 0..2 arrays with no element equal to the product mod 3 of any two of its horizontal and vertical neighbors.at n=5A193499
• Numbers n such that n and n+1 both have 18 divisors.at n=14A274360
• Triangle read by rows: T(n,k) is the number of maximal chains in the poset of all k-ary words of length <= n, ordered by B covers A iff A_i <= B_{i+k} for all i in A and some k >= 0.at n=43A378588