a(n) = 11*4^n.

Terms

a(0) =11a(1) =44a(2) =176a(3) =704a(4) =2816a(5) =11264a(6) =45056a(7) =180224a(8) =720896a(9) =2883584a(10) =11534336a(11) =46137344a(12) =184549376a(13) =738197504a(14) =2952790016a(15) =11811160064a(16) =47244640256a(17) =188978561024a(18) =755914244096