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 A258081 #15 Jun 05 2015 06:33:05 %S A258081 1,1,1,1,2,10,12,10,21,25,70,670,239,2115,586,1619,26800,2505,99019, %T A258081 40903,285641,67166,1852765 %N A258081 Values of k in A071580. %C A258081 The first 23 terms were found using gwnum, and the first 22 have been independently checked using gmp. %H A258081 Mersenne Forum, <a href="http://mersenneforum.org/showthread.php?t=20260">A071580</a> %o A258081 (PARI) terms=12; p=2; for(n=2, terms, q=p+1; while(!ispseudoprime(q), q=q+p); print1(q\p,", "); p=p*q) \\ _Serge Batalov_, May 19 2015 %Y A258081 Cf. A061092, A072532, A113334. %K A258081 nonn,hard,more %O A258081 1,5 %A A258081 _Andrew R. Booker_, May 19 2015