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 A023237 #50 Jul 02 2025 16:01:55
%S A023237 3,7,13,19,31,43,97,103,109,151,157,181,193,211,241,271,337,349,367,
%T A023237 409,421,439,487,523,547,571,601,613,631,691,733,769,811,823,829,883,
%U A023237 937,1009,1021,1033,1039,1063,1069,1117,1201,1249,1279,1291,1459,1483,1489
%N A023237 Primes p such that 10*p + 1 is also prime.
%C A023237 Primes which with a 1 appended stay prime.
%C A023237 Corresponding values of 10n + 1 in A055781. - _Jaroslav Krizek_, Jul 14 2010
%C A023237 Subsequence of A024912. - _Michel Marcus_, May 21 2014
%H A023237 Vincenzo Librandi, <a href="/A023237/b023237.txt">Table of n, a(n) for n = 1..1000</a>
%p A023237 with(numtheory); for i from 1 to 500 do if isprime(10*ithprime(i)+1) then printf(`%d,`, ithprime(i)) fi: od: # _James Sellers_, Apr 09 2005
%t A023237 Select[Prime[Range[ 240]], PrimeQ[FromDigits[Join[IntegerDigits[ # ], {1}]]] &] (* _Robert G. Wilson v_, Apr 09 2005 *)
%t A023237 Select[Prime[Range[900]], PrimeQ[10 # + 1] &] (* _Vincenzo Librandi_, May 21 2014 *)
%o A023237 (Magma) [n: n in [0..1000] | IsPrime(n) and IsPrime(10*n+1)]; // _Vincenzo Librandi_, Nov 20 2010
%o A023237 (Magma) [p: p in PrimesUpTo(1100)| IsPrime(10*p+1)]; // _Vincenzo Librandi_, May 21 2014
%Y A023237 Cf. A024912, A055781, A105435, A005384 (2*p + 1), A158017 (10*p - 1).
%K A023237 nonn,easy
%O A023237 1,1
%A A023237 _David W. Wilson_
%E A023237 Edited by _N. J. A. Sloane_ at the suggestion of _M. F. Hasler_, Aug 24 2007