1412040domain: NAppears in sequencesa(n) = ((n-th prime)^4-(n-th prime)^2)/2.at n=12A138418Let T(n) = n(n+1)/2 be the n-th triangular number (A000217); a(n) = T(8T(n)).at n=20A185096Triangular numbers that are the product of a triangular number and a square number (both greater than 1).at n=21A253650