68178domain: NAppears in sequences24 'Reverse and Add' steps are needed to reach a palindrome.at n=39A065318Sum of numbers that can be written as t*n + u*(n+1) for nonnegative integers t,u in exactly four ways.at n=10A076457a(n) = ceiling((9*(9/4)^n - 4) / 5).at n=13A108870