a(n) = 2*a(n-1)+3 with n>1, a(1)=8.

Terms

a(0) =8a(1) =19a(2) =41a(3) =85a(4) =173a(5) =349a(6) =701a(7) =1405a(8) =2813a(9) =5629a(10) =11261a(11) =22525a(12) =45053a(13) =90109a(14) =180221a(15) =360445a(16) =720893a(17) =1441789a(18) =2883581a(19) =5767165a(20) =11534333a(21) =23068669a(22) =46137341a(23) =92274685a(24) =184549373a(25) =369098749a(26) =738197501a(27) =1476395005a(28) =2952790013