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 A105435 #16 Jul 02 2025 16:02:02
%S A105435 3,7,13,31,37,67,73,79,97,103,109,151,163,181,193,223,229,277,283,307,
%T A105435 367,373,409,433,439,487,499,523,571,601,607,613,619,709,733,787,811,
%U A105435 823,877,907,997,1069,1087,1093,1117,1171,1213,1279,1321,1399,1423,1447
%N A105435 Primes which with a 1 prepended remain prime.
%H A105435 T. D. Noe, <a href="/A105435/b105435.txt">Table of n, a(n) for n = 1..10000</a>
%p A105435 with(numtheory); for i from 1 to 500 do if isprime(10^(ceil(log[10](ithprime(i))))+ithprime(i)) then printf(`%d,`, ithprime(i)) fi: od: # _James Sellers_, Apr 09 2005
%t A105435 Select[ Prime[ Range[ 230]], PrimeQ[ FromDigits[ Join[{1}, IntegerDigits[ # ]]]] &] (* _Robert G. Wilson v_, Apr 09 2005 *)
%t A105435 Select[Prime[Range[250]],PrimeQ[10^IntegerLength[#]+#]&] (* _Harvey P. Dale_, May 30 2023 *)
%Y A105435 Cf. A023237.
%K A105435 nonn,base
%O A105435 1,1
%A A105435 _Lekraj Beedassy_, Apr 08 2005
%E A105435 Corrected and extended by _Robert G. Wilson v_ and _James Sellers_, Apr 09 2005