%I A053866
%S A053866 0,1,1,0,1,0,0,0,1,1,0,0,0,0,0,0,1,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,
%T A053866 0,1,0,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,
%U A053866 0,0,1,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,1,0,0,0,0
%N A053866 Parity of sum of divisors of n.
%H A053866 Michael Gilleland, <a href="selfsimilar.html">Some Self-Similar Integer 
               Sequences</a>
%F A053866 a(n) = A000203(n) mod 2. a(n)=1 iff n>0 is a square or twice a square.
%F A053866 Multiplicative with a(2^e)=1, a(p^e)=1 if e even, 0 otherwise.
%F A053866 Dirichlet g.f.: zeta(2s)(1+2^-s). - Michael Somos Apr 12 2004
%o A053866 (PARI) a(n)=if(n<1,0,issquare(n)|issquare(2*n)) /* Michael Somos Apr 
               12 2004 */
%Y A053866 Cf. A000203, A028982.
%Y A053866 A093709(n)=a(n) if n>0.
%Y A053866 Sequence in context: A079336 A057215 A029691 this_sequence A156595 A143222 
               A010060
%Y A053866 Adjacent sequences: A053863 A053864 A053865 this_sequence A053867 A053868 
               A053869
%K A053866 nonn,mult
%O A053866 0,1
%A A053866 Henry Bottomley (se16(AT)btinternet.com), Mar 29 2000
%E A053866 More terms from James A. Sellers (sellersj(AT)math.psu.edu), Apr 08 2000