a(n) = 2^(n + 3) - 10*n - 6.

Terms

a(0) =0a(1) =6a(2) =28a(3) =82a(4) =200a(5) =446a(6) =948a(7) =1962a(8) =4000a(9) =8086a(10) =16268a(11) =32642a(12) =65400a(13) =130926a(14) =261988a(15) =524122a(16) =1048400a(17) =2096966a(18) =4194108a(19) =8388402a(20) =16777000a(21) =33554206a(22) =67108628a(23) =134217482a(24) =268435200a(25) =536870646a(26) =1073741548a(27) =2147483362a(28) =4294967000a(29) =8589934286