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 A262299 #30 Sep 29 2015 09:15:54 %S A262299 2,13,124567,12356789,123467891011,123457,123456891011 %N A262299 Let S(n) denote the sequence formed by concatenating the decimal numbers 1,2,3,..., omitting n; a(n) is the smallest prime in S(n), or -1 if no term in S(n) is prime. %C A262299 A262300 is now the main entry for this question. %e A262299 a(8) = 1234567910111213...1873 (ending at 1873, a 6384-digit probable prime, and too large to display here) was found by _David Broadhurst_ on Sep 27 2015. %e A262299 a(9) = 1234567810111213141516171819, %e A262299 a(11) = 123456789101213, %e A262299 and a(19) = 12345678910111213141516171820212223242526272829. %e A262299 Sep 28, 2015: _David Broadhurst_ has also found a(10), a(12), a(14), a(16), a(17), a(18), and a(20). See A262300 for their values. %e A262299 a(13) is at present unknown. %Y A262299 A262300 gives the last term in S(n) when a prime appears for the first time. %Y A262299 See A262571-A262582 for the sequences S(1) through S(12). %Y A262299 Cf. A007908 (which plays the role of S(0)). %Y A262299 For the primes in S(1) and S(2) see A089987, A262298. %K A262299 nonn,base,more %O A262299 1,1 %A A262299 _N. J. A. Sloane_ and Jerrold B. Tunnell, Sep 25 2015