202398

Appears in sequences

• G.f.: Sum_{n>=0} n!^2 * x^n / Product_{k=1..n} (1 + k*x)^2.at n=6A216860
• Number of (n+3) X (n+3) 0..2 matrices with each 4 X 4 subblock idempotent.at n=14A224720