a(n) = 10*a(n-2) - 16*a(n-4) for n > 3, a(0) = 1, a(1) = 5, a(2) = 14, a(3) = 34.

Terms

a(0) =1a(1) =5a(2) =14a(3) =34a(4) =124a(5) =260a(6) =1016a(7) =2056a(8) =8176a(9) =16400a(10) =65504a(11) =131104a(12) =524224a(13) =1048640a(14) =4194176a(15) =8388736a(16) =33554176a(17) =67109120a(18) =268434944a(19) =536871424a(20) =2147482624a(21) =4294968320a(22) =17179867136a(23) =34359740416a(24) =137438949376a(25) =274877911040