72127domain: NAppears in sequencesPalindromes of the form 3n + 1 where n is also a palindrome: palindromes arising in A083829.at n=21A083830Palindromes of the form 6n + 1 where n is also a palindrome. palindromes arising in A083835.at n=7A083836Palindromic composite numbers starting with a digit 7.at n=33A222728