212226domain: NAppears in sequencesSmallest triangular number containing exactly n 2's.at n=3A036519Triangular numbers composed of digits {1,2,6}.at n=7A119103a(n) = (m(n)^2 + 3)*(m(n)^2 + 7)/32, where m(n) = 2*n - 1.at n=25A336535Triangular numbers (A000217) in A353729.at n=12A370520