%I A010673
%S A010673 0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,
%T A010673 2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,
%U A010673 0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0,2,0
%N A010673 Period 2.
%C A010673 Euler number (or Euler characteristic) of (n+1)-sphere. - Franz Vrabec 
               (franz.vrabec(AT)aon.at), Sep 07 2007
%C A010673 Submitted A153735=-1,0,0,2,4,10,20,. a(n+1)=A153735(n+1)-2*A153735(n). 
               [From Paul Curtz (bpcrtz(AT)free.fr), Jan 01 2009]
%C A010673 First differences of A109613. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), 
               Dec 05 2009]
%D A010673 R. Carter, G. Segal, I. Macdonald, Lectures on Lie Groups and Lie Algebras, 
               London Mathematical Society Student Texts 32, Cambridge University 
               Press, 1995; see p. 68.
%F A010673 1-(-1^n).
%F A010673 a(n)=2*(n mod 2) - Paolo P. Lava (ppl(AT)spl.at), Oct 20 2006
%Y A010673 Sequence in context: A096972 A101227 A021499 this_sequence A084099 A036665 
               A053472
%Y A010673 Adjacent sequences: A010670 A010671 A010672 this_sequence A010674 A010675 
               A010676
%K A010673 nonn,easy,new
%O A010673 0,2
%A A010673 N. J. A. Sloane (njas(AT)research.att.com).