Partial sums of A007583.

Terms

a(0) =1a(1) =4a(2) =15a(3) =58a(4) =229a(5) =912a(6) =3643a(7) =14566a(8) =58257a(9) =233020a(10) =932071a(11) =3728274a(12) =14913085a(13) =59652328a(14) =238609299a(15) =954437182a(16) =3817748713a(17) =15270994836a(18) =61083979327a(19) =244335917290a(20) =977343669141