20402

Appears in sequences

• Numbers n such that tau(sigma(n))= tau(tau(n)).at n=37A015730
• Numbers k such that k*(k+5) is a palindrome.at n=11A028558
• Palindromes whose sum of divisors is odd.at n=11A028984
• Nonsquare palindromes whose sum of divisors is odd.at n=3A028985
• Base-10 palindromes that start with 2.at n=26A043037
• Palindromic even lucky numbers.at n=25A045960
• Palindromes with exactly 3 palindromic prime factors (counted with multiplicity).at n=19A046377
• a(n) is the smallest palindrome > a(n-1) such that a(1)+a(2)+...+a(n) is a prime.at n=26A051934
• Palindromes with successive increasing difference: a(k)-a(k-1) > a(k+1)- a(k).at n=40A071250
• Palindromic even numbers with exactly 3 prime factors (counted with multiplicity).at n=25A075816
• a(n) = 2*prime(n)^2.at n=25A079704
• a(n) = concatenate(n, A010888(2*n), reverse(n)), where A010888 = digital root.at n=19A082944
• Palindromes in A085932.at n=9A085933
• Palindromes in which the sum of the internal digits = the sum of the external digits.at n=15A088285
• Palindromes n such that 10n01 is a prime.at n=35A099744
• Least inverse of A114912, or -1 if no inverse exists.at n=21A115251
• Number of 3-Carlitz compositions of n (or, more generally p-Carlitz compositions, p > 1), i.e., words b_1^{i_1}b_2^{i_2}...b_k^{i_k} such that the b_j's and i_j's are positive integers for which Sum_{j=1..k} i_j * b_j = n and, for all j, i_j < p and if b_j = b_(j+1) then i_j + i_(j+1) is not equal to p.at n=14A129922
• 2*p^2, for p an odd prime.at n=24A143928
• Terms in A177950 that are not in A002778.at n=39A175440
• Numbers k such that gcd(k^2, reverse(k^2)) = k.at n=13A175823