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 A110054 #16 Sep 07 2025 01:16:30
%S A110054 1,29,47,59,71,73,77,79,83,91,107,109,113,127,137,149,151,161,163,193,
%T A110054 197,199,247,269,289,293,311,317,323,329,337,347,349,361,367,379,389,
%U A110054 403,419,437,461,493,499,511,527,533,553,557,587,601,613,619,643,647
%N A110054 Numbers k such that the string 222k is the decimal expansion of a prime number.
%C A110054 All terms == 1 or 5 (mod 6). - _Robert Israel_, Oct 30 2019
%H A110054 Robert Israel, <a href="/A110054/b110054.txt">Table of n, a(n) for n = 1..10000</a>
%e A110054 1 is in the sequence because 2221 is prime.
%e A110054 91 is in the sequence because 22291 is prime.
%e A110054 109 is in the sequence because 222109 is prime.
%p A110054 select(t -> isprime(222*10^(1+ilog10(t))+t),[seq(seq(6*i+j,j=[1,5]),i=0..1000)]); # _Robert Israel_, Oct 30 2019
%t A110054 Select[Range[1000], PrimeQ[FromDigits[Join[{2, 2, 2}, IntegerDigits[ # ]]]] &] (* _Alonso del Arte_ *)
%t A110054 Select[Range[1000],PrimeQ[222*10^IntegerLength[#]+#]&] (* _Harvey P. Dale_, Oct 13 2024 *)
%o A110054 (Magma) [ n: n in [1..700] | IsPrime(Seqint(Intseq(n) cat [2, 2, 2])) ]; // _Klaus Brockhaus_, Feb 03 2011
%K A110054 nonn,base,changed
%O A110054 1,2
%A A110054 _Parthasarathy Nambi_, Sep 04 2005
%E A110054 More terms from _Alonso del Arte_, Sep 06 2005