2251200domain: NAppears in sequencesa(n) = 1*2*3*4*5 + 6*7*8*9*10 + 11*12*13*14*15 + ... + (up to n).at n=19A319206a(n) = 5*4*3*2*1 + 10*9*8*7*6 + 15*14*13*12*11 + ... + (up to the n-th term).at n=19A319869Table T(n,k) read by upward antidiagonals. T(n,k) = Sum_{i=1..n} Product_{j=1..k} (i-1)*k+j.at n=32A333446