A120145 a(1)=20; a(n)=floor((41+sum(a(1) to a(n-1)))/2).

20, 30, 45, 68, 102, 153, 229, 344, 516, 774, 1161, 1741, 2612, 3918, 5877, 8815, 13223, 19834, 29751, 44627, 66940, 100410, 150615, 225923, 338884, 508326, 762489, 1143734, 1715601, 2573401, 3860102, 5790153, 8685229, 13027844