%I A094958
%S A094958 1,2,4,5,8,10,16,20,32,40,64,80,128,160,256,320,512,640,1024,1280,2048,
%T A094958 2560,4096,5120,8192,10240,16384,20480,32768,40960,65536,81920,131072,
%U A094958 163840,262144,327680,524288,655360,1048576,1310720,2097152
%N A094958 Numbers of the form 2^n or 5*2^n.
%C A094958 The subset {a(1),...,a(2k)} together with a(2k+2) is the set of proper 
               divisors of 5*2^k.
%C A094958 Comment from Wouter Meeussen (wouter.meeussen(AT)pandora.be), Apr 10 
               2005: This appears to be the same sequence as "Numbers n such that 
               n^2 is not the sum of three nonzero squares". Don Reble and Paul 
               Pollack respond: Yes, that is correct.
%C A094958 For a(n)>4: number of vertices of complete graphs that can be properly 
               edge-colored in such a way that the edges can be partitioned into 
               edge disjoint multicolored isomorphic spanning trees.
%C A094958 Also numbers k such that k^2=a^2+b^2+c^2 has no solutions in the positive 
               integers a, b and c. - Wouter Meeussen (wouter.meeussen(AT)pandora.be), 
               Apr 20 2005
%H A094958 G. M. Constantine, <a href="http://www.dmtcs.org/volumes/abstracts/dm050108.abs.html">
               Multicolored parallelisms of isomorphic spanning trees</a>, Discrete 
               Mathematics and Theoretical Computer Science, 5(2002), 121-126.
%F A094958 a(1)=1, a(2)=2, a(3)=4, for n>=0, a(2n+3) = 4*2^n, a(2n+4) = 5*2^n.
%F A094958 Recurrence: for n>4, a(n) = 2a(n-2).
%F A094958 G.f.: [x(1+x)(1+x+x^2)]/[1-2x^2].
%Y A094958 Cf. A029744, A029745. Union of A000079 and A020714.
%Y A094958 Complement of A005767.
%Y A094958 Sequence in context: A133075 A018433 A115831 this_sequence A018565 A018391 
               A018310
%Y A094958 Adjacent sequences: A094955 A094956 A094957 this_sequence A094959 A094960 
               A094961
%K A094958 nonn,easy
%O A094958 1,2
%A A094958 Ralf Stephan, Jun 01 2004