# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a032350 Showing 1-1 of 1 %I A032350 #41 Apr 07 2021 14:40:05 %S A032350 1,4,6,8,9,22,33,44,55,66,77,88,99,111,121,141,161,171,202,212,222, %T A032350 232,242,252,262,272,282,292,303,323,333,343,363,393,404,414,424,434, %U A032350 444,454,464,474,484,494,505,515,525,535,545,555,565,575,585,595,606,616 %N A032350 Palindromic nonprime numbers. %C A032350 Complement of A002385 (palindromic primes) with respect to A002113 (palindromic numbers). - _Jaroslav Krizek_, Mar 12 2013 %C A032350 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 %H A032350 Georg Fischer, Table of n, a(n) for n = 1..10217 %H A032350 W. D. Banks, D. N. Hart, and M. Sakata, Almost all palindromes are composite, Math. Res. Lett., 11 No. 5-6 (2004), 853-868. %H A032350 Patrick De Geest, World!Of Numbers %H A032350 Patrick De Geest, World!Of Palindromic Primes %t A032350 palq[n_] := IntegerDigits[n]==Reverse[IntegerDigits[n]]; Select[Range[700], palq[ # ]&&!PrimeQ[ # ]&] %t A032350 (* Second program: *) %t A032350 Select[Range@ 616, And[PalindromeQ@ #, ! PrimeQ@ #] &] (* _Michael De Vlieger_, Jan 02 2018 *) %o A032350 (Sage) %o A032350 [n for n in (1..616) if not is_prime(n) and Word(n.digits()).is_palindrome()] # _Peter Luschny_, Sep 13 2018 %o A032350 (GAP) Filtered([1..620],n-> not IsPrime(n) and ListOfDigits(n)=Reversed(ListOfDigits(n))); # _Muniru A Asiru_, Mar 08 2019 %Y A032350 Cf. A002113, A002385. %K A032350 easy,nonn,base %O A032350 1,2 %A A032350 _Patrick De Geest_ %E A032350 Edited by _Dean Hickerson_, Oct 22 2002 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE