cp's OEIS Frontend

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.

A318568 Primes p such that 2^p reversed is a prime.

This page as a plain text file.
%I A318568 #27 May 17 2025 22:45:06
%S A318568 5,7,17,37,107,137,271
%N A318568 Primes p such that 2^p reversed is a prime.
%C A318568 Equivalently, primes in A057708. - _Muniru A Asiru_, Dec 25 2018
%C A318568 a(8) > 200000 using A057708. - _Michael S. Branicky_, May 17 2025
%t A318568 Select[Prime[Range[100]], PrimeQ[ToExpression[StringReverse[ToString[2^#]]]] &]
%o A318568 (Magma) [p: p in PrimesUpTo(200) | IsPrime(Seqint(Reverse(Intseq(2^p))))];
%o A318568 (PARI) isok(p) = isprime(p) && isprime(fromdigits(Vecrev(digits(2^p)))); \\ _Michel Marcus_, Sep 22 2018
%o A318568 (GAP) P0:=List(List([1..300],j->Reversed(ListOfDigits(2^j))),k->Sum([1..Size(k)],i->k[i]*10^(Size(k)-i)));;
%o A318568 a:=Filtered([1..Length(P0)],m->IsPrime(m) and IsPrime(P0[m]));; Print(a); # _Muniru A Asiru_, Dec 25 2018
%Y A318568 Cf. A059706.
%Y A318568 Subsequence of A057708.
%K A318568 nonn,base,more
%O A318568 1,1
%A A318568 _Vincenzo Librandi_, Sep 22 2018