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 A359097 #20 Dec 22 2022 08:17:19 %S A359097 1,25,304,3909,58299,907721 %N A359097 Number of distinct primes of type k + reverse(k) when k is a (2n - 1)-digit number. %e A359097 1 + reverse(1) = 2 is prime and for no other 1-digit number k, k + reverse(k) = 2k is prime, thus a(2*1-1) = a(1) = 1. %o A359097 (PARI) %o A359097 R(k)=fromdigits(Vecrev(digits(k))) %o A359097 a(n)=my(m=2*n-1,u=Set([]),mmin=10^(m-1),mmax=10^m-1,card=0);for(m=mmin,mmax,y=m+R(m);if(isprime(y)&&!setsearch(u,y),u=Set(concat(u,y));card++));card %Y A359097 Cf. A358985, A056964, A067030, A358986. %K A359097 nonn,base,more %O A359097 1,2 %A A359097 _Jean-Marc Rebert_, Dec 16 2022