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%I #30 Apr 02 2020 19:31:03
%S 2,3,5,7,23,29,31,37,53,59,71,73,79,211,223,227,229,233,239,241,251,
%T 257,263,269,271,277,281,283,293,307,311,313,317,331,337,347,349,353,
%U 359,367,373,379,383,389,397,503,509,521,523,541,547,557,563,569,571
%N Primes whose first digit is prime.
%H Robert Israel, <a href="/A320585/b320585.txt">Table of n, a(n) for n = 1..10000</a>
%p 2,3,5,7,seq(seq(op(select(isprime,[seq(i*10^(d-1)+j,j=1..10^(d-1)-1,2)])),i=[2,3,5,7]),d=1..4); # _Robert Israel_, Apr 02 2020
%t Select[Range[575], PrimeQ[#] && PrimeQ[IntegerDigits[#][[1]]] &] (* _Amiram Eldar_, Nov 11 2018 *)
%o (PARI) isok(n) = isprime(n) && isprime(digits(n)[1]); \\ _Michel Marcus_, Oct 17 2018
%Y Intersection of A000040 and A320584 (numbers whose first digit is prime).
%K nonn,base
%O 1,1
%A _Kritsada Moomuang_, Oct 16 2018
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