a(n) = 36*Fibonacci(2*n+1) - 4.

Terms

a(0) =32a(1) =68a(2) =176a(3) =464a(4) =1220a(5) =3200a(6) =8384a(7) =21956a(8) =57488a(9) =150512a(10) =394052a(11) =1031648a(12) =2700896a(13) =7071044a(14) =18512240a(15) =48465680a(16) =126884804a(17) =332188736a(18) =869681408a(19) =2276855492a(20) =5960885072a(21) =15605799728a(22) =40856514116a(23) =106963742624a(24) =280034713760a(25) =733140398660