T(n,n+1) + T(n,n+2) + ... + T(n,2n), T given by A027113.

Terms

a(0) =2a(1) =7a(2) =23a(3) =72a(4) =218a(5) =648a(6) =1907a(7) =5581a(8) =16290a(9) =47502a(10) =138521a(11) =404183a(12) =1180402a(13) =3450899a(14) =10099605a(15) =29589780a(16) =86781374a(17) =254761882a(18) =748580729a(19) =2201465799a(20) =6479301022a(21) =19083705249a(22) =56246157177a(23) =165881453558a(24) =489506759446