%I A106511
%S A106511 1,0,0,0,1,2,3,4,6,10,17,28,45,72,116,188,305,494,799,1292,2090,3382,
%T A106511 5473,8856,14329,23184,37512,60696,98209,158906,257115,416020,673134,
%U A106511 1089154,1762289,2851444,4613733,7465176,12078908,19544084,31622993
%V A106511 1,0,0,0,1,-2,3,-4,6,-10,17,-28,45,-72,116,-188,305,-494,799,-1292,2090,
               -3382,5473,
%W A106511 -8856,14329,-23184,37512,-60696,98209,-158906,257115,-416020,673134,-1089154,
               1762289,
%X A106511 -2851444,4613733,-7465176,12078908,-19544084,31622993
%N A106511 Expansion of (1+x)^2/((1+x+x^2)(1+x-x^2)).
%C A106511 Diagonal sums of the Riordan array ((1+x)/(1+x+x^2),x/(1+x)), A106509.
%F A106511 a(n)=sum{k=0..floor(n/2), sum{j=0..n-2k, (-1)^j*binomial(2n-3k-j, j)}}
%F A106511 (1/2) [(-1)^n*Fibonacci(n) + kronecker(-3,n) ]. - Ralf Stephan, Jun 2 
               2007
%Y A106511 Cf. A024490.
%Y A106511 Cf. A011646, A039834.
%Y A106511 Sequence in context: A103599 A026502 A060163 this_sequence A024490 A056469 
               A004047
%Y A106511 Adjacent sequences: A106508 A106509 A106510 this_sequence A106512 A106513 
               A106514
%K A106511 easy,sign
%O A106511 0,6
%A A106511 Paul Barry (pbarry(AT)wit.ie), May 04 2005