a(n) = 87*2^n - 38 (n>=0).

Terms

a(0) =49a(1) =136a(2) =310a(3) =658a(4) =1354a(5) =2746a(6) =5530a(7) =11098a(8) =22234a(9) =44506a(10) =89050a(11) =178138a(12) =356314a(13) =712666a(14) =1425370a(15) =2850778a(16) =5701594a(17) =11403226a(18) =22806490a(19) =45613018a(20) =91226074a(21) =182452186a(22) =364904410a(23) =729808858a(24) =1459617754a(25) =2919235546a(26) =5838471130a(27) =11676942298a(28) =23353884634a(29) =46707769306