The sum of the lengths of all weighted lattice paths in L_n.

Terms

a(0) =0a(1) =1a(2) =3a(3) =11a(4) =33a(5) =96a(6) =278a(7) =787a(8) =2205a(9) =6133a(10) =16941a(11) =46554a(12) =127390a(13) =347331a(14) =944121a(15) =2559607a(16) =6923529a(17) =18690138a(18) =50364988a(19) =135506485a(20) =364063815a(21) =976880631a(22) =2618206923a(23) =7009868646a(24) =18749876418a(25) =50107633501a(26) =133800148323a(27) =357012426677a(28) =951936494055