Partial sums of A056272.

Terms

a(0) =1a(1) =3a(2) =8a(3) =23a(4) =75a(5) =277a(6) =1132a(7) =4977a(8) =22979a(9) =109451a(10) =531456a(11) =2610931a(12) =12917683a(13) =64181625a(14) =319695980a(15) =1594859885a(16) =7963472187a(17) =39784944799a(18) =198827606704a(19) =993846943839