%I A001621
%S A001621 0,2,12,42,110,240,462,812,1332,2070,3080,4422,6162,8372,
%T A001621 11130,14520,18632,23562,29412,36290,44310,53592,64262,
%U A001621 76452,90300,105950,123552,143262,165242,189660,216690
%N A001621 n*(n+1)*(n^2+n+2)/4.
%C A001621 Number of integer sequences of length n+1 with sum zero and sum of absolute 
               values 4. [From Ron Hardin (rhhardin(AT)att.net), Feb 22 2009]
%F A001621 G.f.:(-2*x*(x^2+x+1))/(x-1)^5 [From Maksym Voznyy (voznyy(AT)mail.ru), 
               Jul 27 2009]
%p A001621 a:=n->add(n+add(binomial(n,2), j=1..n),j=2..n):seq(a(n)/2, n=1..35); 
               [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 26 2008]
%p A001621 with(finance):seq(add(cashflows([k^3, k, 0], 0 ), k=0..n), n=0..45); 
               # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 22 2008]
%t A001621 a[n_]:=Sum[i+i^3, {i, 1, n}]; [From Vladimir Orlovsky (4vladimir(AT)gmail.com), 
               Dec 05 2008]
%Y A001621 Equals 2 * A002817 and [A058919(n-1)-1]/2.
%Y A001621 A092365 [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 26 2008]
%Y A001621 Sequence in context: A127725 A048014 A094702 this_sequence A055681 A111389 
               A013704
%Y A001621 Adjacent sequences: A001618 A001619 A001620 this_sequence A001622 A001623 
               A001624
%K A001621 nonn
%O A001621 0,2
%A A001621 N. J. A. Sloane (njas(AT)research.att.com).