cp's OEIS Frontend

A228445 Prime numbers with a binary representation in which each digit is repeated at most twice.

%I A228445 #22 May 08 2022 23:03:16
%S A228445 2,3,5,11,13,19,37,41,43,53,73,83,89,101,107,109,149,173,179,181,211,
%T A228445 293,307,331,347,409,421,587,601,613,617,619,659,661,677,683,691,809,
%U A228445 811,821,853,857,859,877,1171,1193,1229,1237,1321,1381,1427,1429,1433,1451,1453,1459,1609,1613,1619,1621,1627,1637,1709,1741
%N A228445 Prime numbers with a binary representation in which each digit is repeated at most twice.
%F A228445 A000040 INTERSECT A063037.
%e A228445 13 belongs to the list as its binary representation is 1101, in which the first group of 1 consists of 2 repetitions, the first group of 0 consists of only one item and the second group of 1 consists still of only one item; 73 belongs to the list as its binary representation is 1001001, in which 1 is never repeated and 0 is repeated two times.
%p A228445 isA228445 := proc(n)
%p A228445     isprime(n) and isA063037(n) ;
%p A228445 end proc:
%p A228445 for n from 1 to 2000 do
%p A228445     if isA228445(n) then
%p A228445         printf("%d,",n) ;
%p A228445     end if;
%p A228445 end do: # _R. J. Mathar_, Dec 18 2013
%t A228445 Select[Prime[Range[300]],Max[Length/@Split[IntegerDigits[#,2]]]<3&] (* _Harvey P. Dale_, May 24 2015 *)
%Y A228445 Cf. A000040, A063037.
%K A228445 nonn,base
%O A228445 1,1
%A A228445 _Pierandrea Formusa_, Nov 06 2013