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 A171658 #11 Jan 03 2022 20:43:01 %S A171658 155921,5649221,6726821,8598221,8825321,9953621,10303721,11948021, %T A171658 12117121,14645921,14821721,14866421,15275021,17270621,17524921, %U A171658 18497321,19193921,19731821,20741621,21721621,22170221,23009521,24257921,24579221,24919721 %N A171658 Primes ending with the digits 21 which are the only primes in their century. %C A171658 Primes of the form 100*k+21 with no other prime of the form 100*k+j for j=1 to 99 with the same k. %C A171658 Thanks for the assistance and research of John Moyer. There is likely an infinite number of such primes. %e A171658 a(1)=155921 is prime and it is the only prime between 155900 and 156000. %Y A171658 Cf. A164987. %K A171658 nonn,base %O A171658 1,1 %A A171658 _Ki Punches_, Dec 14 2009 %E A171658 Definition detailed and more terms appended by _R. J. Mathar_, Oct 09 2010