a(n) = 75*2^n - 38.

Terms

a(0) =37a(1) =112a(2) =262a(3) =562a(4) =1162a(5) =2362a(6) =4762a(7) =9562a(8) =19162a(9) =38362a(10) =76762a(11) =153562a(12) =307162a(13) =614362a(14) =1228762a(15) =2457562a(16) =4915162a(17) =9830362a(18) =19660762a(19) =39321562a(20) =78643162a(21) =157286362a(22) =314572762a(23) =629145562a(24) =1258291162a(25) =2516582362a(26) =5033164762a(27) =10066329562a(28) =20132659162a(29) =40265318362