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 A237263 #32 Feb 03 2023 01:35:57 %S A237263 2,31,19,23,139,6089,40949,13153513,748105003,11307204673, %T A237263 202073177599,14740352606699 %N A237263 Smallest prime such that if up to n copies of the final digit are appended to the number, it remains prime, but it does not for n+1 copies. %H A237263 D. J. Broadhurst et al., <a href="https://groups.yahoo.com/neo/groups/primenumbers/conversations/topics/25454">Prime Numbers and Primality Testing, Topic 25454</a>, Yahoo Groups, 2014 %H A237263 David Broadhurst, Kevin Acres, Mark Underwood, <a href="/A237263/a237263.txt">Base-10 puzzle</a>, digest of 6 messages in primenumbers Yahoo group, Jan 16 - Feb 1, 2014. %e A237263 23 is prime, so are 233, 2333, 23333, but not 233333 = 353 * 661. No prime smaller than 23 has this property for n = 3, so a(3) = 23. %K A237263 nonn,base,more %O A237263 0,1 %A A237263 _Claudio Meller_, Feb 05 2014 %E A237263 a(1)-a(10) from _David Broadhurst_, Feb 01 2014 %E A237263 a(11) from _Giovanni Resta_, Feb 06 2014