%I A117374
%S A117374 1,3,1,4,4,5,8,9,13,17,22,30,39,52,69,91,121,160,212,281,372,493,653,
%T A117374 865,1146,1518,2011,2664,3529,4675,6193,8204,10868,14397,19072,25265,
%U A117374 33469
%V A117374 1,-3,1,-4,4,-5,8,-9,13,-17,22,-30,39,-52,69,-91,121,-160,212,-281,372,
               -493,653,-865,
%W A117374 1146,-1518,2011,-2664,3529,-4675,6193,-8204,10868,-14397,19072,-25265,
               33469
%N A117374 Expansion of (1-3x)/(1-x^2+x^3).
%C A117374 Diagonal sums of number triangle A117372.
%F A117374 a(n)=a(n-2)+a(n-3); a(n)=sum{k=0..floor(n/2), (-1)^n*(C(k,n-2k)+3*C(k, 
               n-2k-1))}.
%Y A117374 Sequence in context: A099813 A141300 A014388 this_sequence A021322 A036412 
               A016473
%Y A117374 Adjacent sequences: A117371 A117372 A117373 this_sequence A117375 A117376 
               A117377
%K A117374 easy,sign
%O A117374 0,2
%A A117374 Paul Barry (pbarry(AT)wit.ie), Mar 10 2006