Partial sums of A003418 starting summing from A003418(1), with a(0) = 0.

Terms

a(0) =0a(1) =1a(2) =3a(3) =9a(4) =21a(5) =81a(6) =141a(7) =561a(8) =1401a(9) =3921a(10) =6441a(11) =34161a(12) =61881a(13) =422241a(14) =782601a(15) =1142961a(16) =1863681a(17) =14115921a(18) =26368161a(19) =259160721a(20) =491953281a(21) =724745841a(22) =957538401a(23) =6311767281a(24) =11665996161a(25) =38437140561a(26) =65208284961a(27) =145521718161a(28) =225835151361