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 A050712 #14 Oct 15 2019 15:14:48 %S A050712 17,23,27,29,41,51,53,77,81,83,87,89,99,127,133,139,141,157,171,181, %T A050712 183,189,193,207,213,219,229,261,271,277,291,307,309,331,333,337,343, %U A050712 349,361,403,421,423,427,433,477,481,489,493,499,501,507,511,517,523 %N A050712 Inserting a digit '2' between adjacent digits of n makes a prime. %H A050712 Harvey P. Dale, <a href="/A050712/b050712.txt">Table of n, a(n) for n = 1..1001</a> %e A050712 333 becomes 3(2)3(2)3 which is prime 32323. %t A050712 Select[Range[10,600],PrimeQ[FromDigits[Riffle[IntegerDigits[#],2]]]&] (* _Harvey P. Dale_, Sep 13 2014 *) %Y A050712 Cf. A050674, A050711, A050713, A050714, A050715, A050716, A050717, A050718, A050719. %K A050712 nonn,base %O A050712 1,1 %A A050712 _Patrick De Geest_, Aug 15 1999 %E A050712 Offset changed to 1 by _Georg Fischer_, Oct 15 2019