This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A256623 #22 Aug 10 2015 17:23:29 %S A256623 4,5,29,102,796,4769,35905,267789,2101184,16809690,137487157, %T A256623 1147385627,9745119882 %N A256623 Number of distinct n-digit patterns in base 10 such that the pattern and its reverse are prime. %C A256623 Here, distinct numbers means under reversal. 13 and 31 are the same pattern under reversal and only count as one. The sequence can be calculated from the number of palindrome primes (A016115), p_i, and number of reversal primes (A048054), r_i. X_i = (r_i - p_i)/2 + p_i. The (r_i - p_i) term is always even, by construction (it is the count of reversible primes that are not their own reverse). %C A256623 This sequence is the set cardinality of the prime numbers under a base-10 digit reversal identity operator. %C A256623 Since there are no palindrome primes with even digits > 11 we know that the even entries are the same as half the number of reversible primes. %F A256623 a(n) = (A048054(n) + A016115(n))/2. %Y A256623 Cf. A016115, A048054. %K A256623 nonn,base,more %O A256623 1,1 %A A256623 _Russell Y. Webb_, Jul 11 2015 %E A256623 a(11)-a(13) from _Giovanni Resta_, Jul 19 2015