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 A050715 #13 Oct 15 2019 15:14:20 %S A050715 11,17,21,27,33,39,47,57,63,69,71,77,83,87,89,93,103,129,139,141,151, %T A050715 159,189,199,207,213,223,237,243,247,267,279,291,301,303,309,313,319, %U A050715 321,327,333,373,379,381,391,403,429,453,457,469,471,477,483,493,499 %N A050715 Inserting a digit '5' between adjacent digits of n makes a prime. %H A050715 Harvey P. Dale, <a href="/A050715/b050715.txt">Table of n, a(n) for n = 1..1001</a> %e A050715 373 becomes 3(5)7(5)3 which is prime 35753. %t A050715 Select[Range[10,500],PrimeQ[FromDigits[Riffle[IntegerDigits[#],5]]]&] (* _Harvey P. Dale_, Apr 07 2018 *) %Y A050715 Cf. A050674, A050711, A050712, A050713, A050714, A050716, A050717, A050718, A050719. %K A050715 nonn,base %O A050715 1,1 %A A050715 _Patrick De Geest_, Aug 15 1999 %E A050715 Offset changed to 1 by _Georg Fischer_, Oct 15 2019