a(n) = 37*2^(n-1)-1.

Terms

a(0) =36a(1) =73a(2) =147a(3) =295a(4) =591a(5) =1183a(6) =2367a(7) =4735a(8) =9471a(9) =18943a(10) =37887a(11) =75775a(12) =151551a(13) =303103a(14) =606207a(15) =1212415a(16) =2424831a(17) =4849663a(18) =9699327a(19) =19398655a(20) =38797311a(21) =77594623a(22) =155189247a(23) =310378495a(24) =620756991a(25) =1241513983a(26) =2483027967a(27) =4966055935