359026206domain: NAppears in sequencesa(0) = 2; for n >= 0, a(n+1) = a(n)*(a(n)+1)/2.at n=6A007501Triply triangular numbers.at n=21A064322Quadruply triangular numbers.at n=6A066370Least nontrivial n-tuply triangular number.at n=5A096662