a(n) = 5*a(n-2) for n > 2; a(1) = 3, a(2) = 5.

Terms

a(0) =3a(1) =5a(2) =15a(3) =25a(4) =75a(5) =125a(6) =375a(7) =625a(8) =1875a(9) =3125a(10) =9375a(11) =15625a(12) =46875a(13) =78125a(14) =234375a(15) =390625a(16) =1171875a(17) =1953125a(18) =5859375a(19) =9765625a(20) =29296875a(21) =48828125a(22) =146484375a(23) =244140625a(24) =732421875a(25) =1220703125a(26) =3662109375a(27) =6103515625a(28) =18310546875