326011

Appears in sequences

• Number of permutations of up to n kinds of objects, where each kind of object can occur at most two times.at n=5A003011
• A(n,k) = Sum_{i_1=0..n} Sum_{i_2=0..n} ... Sum_{i_k=0..n} multinomial(i_1 + i_2 + ... + i_k; i_1, i_2, ..., i_k), square array A(n,k) read by antidiagonals, for n >= 0, k >= 0.at n=30A308292