%I #4 Mar 30 2012 17:30:18
%S 2,6,18,42,69,126,207,378,621,906,1311,1863,2718,3825,4509,5589,8154,
%T 11475,13527,16767,20130,24909,30894,36078,40581,50301,60390,72675,
%U 85671,92682,107910,118503,121743,150903
%N (s(n)+s(n+1))/6, where s()=A006521.
%K nonn
%O 2,1
%A _Robert G. Wilson v_