266737domain: NAppears in sequencesNumbers k such that k*(k+4) is a palindrome.at n=23A028555a(0) = 16, after which, if (2*a(n-1)) - 1 = product_{k >= 1} (p_k)^(c_k) then a(n) = product_{k >= 1} (p_{k-1})^(c_k), where p_k indicates the k-th prime, A000040(k).at n=34A246345