a(n) = 8*(2^n + 1).

Terms

a(0) =16a(1) =24a(2) =40a(3) =72a(4) =136a(5) =264a(6) =520a(7) =1032a(8) =2056a(9) =4104a(10) =8200a(11) =16392a(12) =32776a(13) =65544a(14) =131080a(15) =262152a(16) =524296a(17) =1048584a(18) =2097160a(19) =4194312a(20) =8388616a(21) =16777224a(22) =33554440a(23) =67108872a(24) =134217736a(25) =268435464a(26) =536870920a(27) =1073741832a(28) =2147483656a(29) =4294967304