a(n) = T(7,n), array T given by A048483.

Terms

a(0) =1a(1) =9a(2) =25a(3) =57a(4) =121a(5) =249a(6) =505a(7) =1017a(8) =2041a(9) =4089a(10) =8185a(11) =16377a(12) =32761a(13) =65529a(14) =131065a(15) =262137a(16) =524281a(17) =1048569a(18) =2097145a(19) =4194297a(20) =8388601a(21) =16777209a(22) =33554425a(23) =67108857a(24) =134217721a(25) =268435449a(26) =536870905a(27) =1073741817a(28) =2147483641a(29) =4294967289