OFFSET
1,2
COMMENTS
Complement of A002385 (palindromic primes) with respect to A002113 (palindromic numbers). - Jaroslav Krizek, Mar 12 2013
Banks, Hart, and Sakata derive a nontrivial upper bound for the number of prime palindromes n <= x as x tends to infinity. It follows that almost all palindromes are composite. The results hold in any base. The authors use Weil's bound for Kloosterman sums. - Jonathan Sondow, Jan 02 2018
LINKS
Georg Fischer, Table of n, a(n) for n = 1..10217
W. D. Banks, D. N. Hart, and M. Sakata, Almost all palindromes are composite, Math. Res. Lett., 11 No. 5-6 (2004), 853-868.
Patrick De Geest, World!Of Numbers
Patrick De Geest, World!Of Palindromic Primes
MATHEMATICA
palq[n_] := IntegerDigits[n]==Reverse[IntegerDigits[n]]; Select[Range[700], palq[ # ]&&!PrimeQ[ # ]&]
(* Second program: *)
Select[Range@ 616, And[PalindromeQ@ #, ! PrimeQ@ #] &] (* Michael De Vlieger, Jan 02 2018 *)
PROG
(Sage)
[n for n in (1..616) if not is_prime(n) and Word(n.digits()).is_palindrome()] # Peter Luschny, Sep 13 2018
(GAP) Filtered([1..620], n-> not IsPrime(n) and ListOfDigits(n)=Reversed(ListOfDigits(n))); # Muniru A Asiru, Mar 08 2019
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
EXTENSIONS
Edited by Dean Hickerson, Oct 22 2002
STATUS
approved