Partial sums of A002893.

Terms

a(0) =1a(1) =4a(2) =19a(3) =112a(4) =751a(5) =5404a(6) =40573a(7) =313408a(8) =2471167a(9) =19791004a(10) =160459069a(11) =1313922064a(12) =10847561089a(13) =90174127684a(14) =754009158019