218743domain: NAppears in sequencesNumber of idempotent n X n 0..4 matrices of rank n-1.at n=6A224329T(n,k)=Number of idempotent n X n 0..k matrices of rank n-1.at n=51A224333Number of idempotent 7 X 7 0..n matrices of rank 6.at n=3A224338