Partial sums of A001334.

Terms

a(0) =1a(1) =7a(2) =37a(3) =175a(4) =793a(5) =3523a(6) =15469a(7) =67351a(8) =291481a(9) =1255615a(10) =5388781a(11) =23057719a(12) =98412925a(13) =419147611a(14) =1781938861a(15) =7563704443a(16) =32061034765a(17) =135735002647a(18) =574031742241