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