%I A087207
%S A087207 0,1,2,1,4,3,8,1,2,5,16,3,32,9,6,1,64,3,128,5,10,17,256,3,4,33,2,9,512,
%T A087207 7,1024,1,18,65,12,3,2048,129,34,5,4096,11,8192,17,6,257,16384,3,8,5,66,
%U A087207 33,32768,3,20,9,130,513,65536,7,131072,1025,10,1,36,19,262144,65,258
%N A087207 A binary representation of the primes that divide a number.
%C A087207 The binary representation of a(n) shows which prime numbers divide n, 
               but not the multiplicities. a(2)=1, a(3)=10, a(4)=1, a(5)=100, a(6)=11, 
               a(10)=101, a(30)=111, etc.
%H A087207 T. D. Noe, <a href="b087207.txt">Table of n, a(n) for n=1..1000</a>
%F A087207 Additive with a(p^e) = 2^pi(p-1). - Vladeta Jovovic (vladeta(AT)eunet.rs), 
               Oct 29 2003
%F A087207 a(n) gives the m such that A019565(m) = A007947(n). - Naohiro Nomoto
%F A087207 A000120(a(n)) = A001221(n); a(n) = Sum(2^(A049084(p)-1): p prime-factor 
               of n). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Nov 
               30 2003
%F A087207 G.f. sum(k>=1, 2^(k-1)*x^prime(k)/(1-x^prime(k)). [From Franklin T. Adams-Watters 
               (FrankTAW(AT)Netscape.net), Sep 01 2009]
%e A087207 a(140) = 13, binary 1101 because 140 is divisible by the first, third 
               and fourth primes and 2^(1-1) + 2^(3-1) + 2^(4-1) = 13.
%Y A087207 Cf. A000040.
%Y A087207 Sequence in context: A138236 A058354 A085930 this_sequence A074987 A128280 
               A106625
%Y A087207 Adjacent sequences: A087204 A087205 A087206 this_sequence A087208 A087209 
               A087210
%K A087207 nonn,nice
%O A087207 1,3
%A A087207 Mitch Cervinka (puritan(AT)planetkc.com), Oct 26 2003
%E A087207 More terms from Don Reble (djr(AT)nk.ca), Ray Chandler (rayjchandler(AT)sbcglobal.net) 
               and Naohiro Nomoto (pcmusume(AT)alpha-net.ne.jp), Oct 28 2003