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 A050713 #15 Dec 23 2023 16:01:37 %S A050713 11,17,19,23,29,31,37,41,43,49,61,73,79,89,97,103,107,131,137,139,157, %T A050713 163,181,191,193,209,211,233,239,241,251,257,259,263,281,283,307,331, %U A050713 353,367,379,391,397,407,413,427,431,463,493,521,523,529,547,563,569 %N A050713 Inserting a digit '3' between adjacent digits of n makes a prime. %H A050713 Harvey P. Dale, <a href="/A050713/b050713.txt">Table of n, a(n) for n = 1..1000</a> %e A050713 407 becomes 4(3)0(3)7 which is prime 43037. %t A050713 Select[Range[10,600],PrimeQ[FromDigits[Riffle[IntegerDigits[#],3]]]&] (* _Harvey P. Dale_, Dec 23 2023 *) %Y A050713 Cf. A050674, A050711, A050712, A050714, A050715, A050716, A050717, A050718, A050719. %K A050713 nonn,base %O A050713 1,1 %A A050713 _Patrick De Geest_, Aug 15 1999