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 A189556 #6 Mar 30 2012 17:22:58 %S A189556 31,61,71,101,103,131,199,211,241,269,359,401,421,433,439,571,619,641, %T A189556 661,719,727,739,751,761,811,1019,1051,1063,1193,1277,1279,1303,1307, %U A189556 1321,1451,1471,1499,1613,1619,1667,1697,1721,1723,1783,1879,1949 %N A189556 Prime numbers n such that x' = n has two solutions, where x' is the arithmetic derivative (A003415) of x. %C A189556 The primes in A189555. %Y A189556 Cf. A003415. %K A189556 nonn %O A189556 1,1 %A A189556 _T. D. Noe_, Apr 24 2011