102020domain: NAppears in sequencesNumbers k such that k^2 + 1 is a palindrome.at n=14A027719Numbers <= 10^6 with valid Luhn mod 10 check digit, sorted first by check digit, then lexicographically.at n=23A249855Numbers with digits in {0,1,2} such that every other digit is strictly less than its neighbors.at n=36A306105