a(n) = 348*2^n - 188.

Terms

a(0) =160a(1) =508a(2) =1204a(3) =2596a(4) =5380a(5) =10948a(6) =22084a(7) =44356a(8) =88900a(9) =177988a(10) =356164a(11) =712516a(12) =1425220a(13) =2850628a(14) =5701444a(15) =11403076a(16) =22806340a(17) =45612868a(18) =91225924a(19) =182452036a(20) =364904260a(21) =729808708a(22) =1459617604a(23) =2919235396a(24) =5838470980a(25) =11676942148a(26) =23353884484