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 A089323 #7 Dec 05 2013 19:56:35 %S A089323 1,3,21,33,1083,2541,51282,51282,1296060612,43449172767,189324538095 %N A089323 Smallest k such that concatenation of r*k and 1 is a prime for all r = 1 to n, or smallest k such that 10*r*k +1 is a prime for all r = 1 to n. %C A089323 The primes arising in triangular form are %C A089323 11 %C A089323 31 61 %C A089323 211 421 631 %C A089323 331 661 991 1321 %C A089323 ... %C A089323 Next term is > 1.38*10^12. - _David Wasserman_, Sep 13 2005 %K A089323 base,hard,nonn %O A089323 1,2 %A A089323 _Amarnath Murthy_, Nov 03 2003 %E A089323 More terms from _Ray G. Opao_, Jan 13 2005 %E A089323 3 more terms from _David Wasserman_, Sep 13 2005