A087530 - OEIS

%I #15 Sep 20 2024 23:54:52

%S 53,35553533,53355353,53533553,3335553553,3355335553,3355355533,

%T 3355533553,3355535353,3535355353,3553535353,3553555333,3555353353,

%U 3555353533,3555533533,5353353553,5353533553,5353553533,5355353533,5355533353,5533553353,5535535333

%N Primes consisting only of digits 3 and 5 occurring with equal frequency.

%C There are 18 digit pairs which can produce such primes. (1,0),(1,3),(1,4),(1,6),(1,7),(1,9),(2,3),(2,9),(3,4),(3,5),(3,7),(3,8),(4,7),(4,9),(5,9),(6,7),(7,9),(8,9).

%H Harvey P. Dale, <a href="/A087530/b087530.txt">Table of n, a(n) for n = 1..5000</a>

%t Sort[Select[FromDigits/@Flatten[Permutations/@Table[PadRight[{},2n,{3,5}],{n,5}],1],PrimeQ]] (* _Harvey P. Dale_, Oct 24 2012 *)

%o (PARI)  \\ Needs B() from A087510.

%o concat(vector(6,k,B(k,3,5,isprime))) \\ _Andrew Howroyd_, Sep 20 2024

%Y Cf. A087510, A087511, A087529.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_ and _Paul D. Hanna_, Sep 12 2003

%E Edited by _Charles R Greathouse IV_, Oct 28 2009