cp's OEIS Frontend

A281227 Primes whose binary reflected Gray code representation is also the decimal representation of a prime.

%I A281227 #12 Jun 13 2025 18:16:55
%S A281227 2,53,233,281,397,521,613,673,733,773,797,829,1049,1129,1433,1553,
%T A281227 1697,1933,2129,2237,2273,2281,2437,2521,2557,2617,2729,2969,3121,
%U A281227 3181,3413,3457,3517,3637,3709,3761,3881,4337,4357,4729,4733,4877,4889,5101,5657,5813,5857,6113,6133
%N A281227 Primes whose binary reflected Gray code representation is also the decimal representation of a prime.
%H A281227 Indranil Ghosh, <a href="/A281227/b281227.txt">Table of n, a(n) for n = 1..481</a>
%e A281227 521 is in the sequence because 521_10 = 1100001101_2 and both 521 and 1100001101 are prime numbers in base 10.
%o A281227 (Python)
%o A281227 from sympy import isprime
%o A281227 def gray(n):
%o A281227     return bin(n^(n//2))[2:]
%o A281227 i=1
%o A281227 j=1
%o A281227 while j<=481:
%o A281227     if isprime(i)==True and isprime(int(gray(i)))==True:
%o A281227         print(str(j)+" "+str(i))
%o A281227         j+=1
%o A281227     i+=1
%Y A281227 Cf. A014550, A065720, A065721, A065722, A065723, A065724.
%K A281227 nonn,base
%O A281227 1,1
%A A281227 _Indranil Ghosh_, Jan 18 2017