644680domain: NAppears in sequencesTriangular numbers with only even digits.at n=28A117978Triangular numbers whose sum of divisors is an oblong number.at n=17A317478Triangle read by rows: T(n, k) is the number of k-dimensional subspaces in (F_9)^n, counted up to coordinate permutation (n >= 0, 0 <= k <= n).at n=24A347975