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Scan the primes, record digit-sum if it is itself prime.
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%I #5 Oct 17 2020 18:15:52

%S 2,3,5,7,2,5,11,5,7,11,7,13,11,17,2,5,5,11,13,7,13,11,17,11,13,17,19,

%T 7,11,13,7,11,17,11,13,5,7,11,7,13,11,17,13,19,19,5,13,7,11,17,11,13,

%U 17,19,17,13,19,17,23,7,13,11,13,17,13,17,17,13,19,13,19,17,23,17,11,13

%N Scan the primes, record digit-sum if it is itself prime.

%e a(13)=5 since the 13th prime is 41 and 4+1=5, which is prime.

%p dig := X->convert((convert(X,base,10)),`+`); a := n->`if`(isprime(dig(ithprime(n)))=true,dig(ithprime(n)),printf(""));

%t Select[Total[IntegerDigits[#]]&/@Prime[Range[200]],PrimeQ] (* _Harvey P. Dale_, Oct 17 2020 *)

%Y Cf. A046704.

%K easy,nonn,base

%O 1,1

%A Francois Jooste (phukraut(AT)hotmail.com), Mar 10 2002