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 A117159 #14 Feb 08 2021 02:56:19 %S A117159 2,3,5,7,13,17,31,37,43,53,71,73,113,131,137,151,157,173,211,223,311, %T A117159 317,359,367,389,431,557,571,593,673,751,827,839,929,953,983,1117, %U A117159 1151,1153,1171,1223,1279,1297,1367,1447,1511,1531,1553,1571,1579,1597,1621 %N A117159 Prime numbers for which the multiplicative digital root is also a prime number. %H A117159 Amiram Eldar, <a href="/A117159/b117159.txt">Table of n, a(n) for n = 1..10000</a> %e A117159 157 is in the sequence because it is a prime number and its multiplicative digital root 5 is also a prime number. %t A117159 a[n_]:=NestWhile[Times@@IntegerDigits[#]&,n,#>9&]; Select[Prime[Range[258]],PrimeQ[a[#]]&] (* _Jayanta Basu_, Jun 02 2013 *) %Y A117159 Intersection of A000040 and A028843. %Y A117159 Cf. A031347. %K A117159 base,nonn %O A117159 1,1 %A A117159 Luc Stevens (lms022(AT)yahoo.com), Apr 21 2006; corrected Apr 30 2006