a(n) = 5*a(n-2), starting 1,2.

Terms

a(0) =1a(1) =2a(2) =5a(3) =10a(4) =25a(5) =50a(6) =125a(7) =250a(8) =625a(9) =1250a(10) =3125a(11) =6250a(12) =15625a(13) =31250a(14) =78125a(15) =156250a(16) =390625a(17) =781250a(18) =1953125a(19) =3906250a(20) =9765625a(21) =19531250a(22) =48828125a(23) =97656250a(24) =244140625a(25) =488281250a(26) =1220703125a(27) =2441406250a(28) =6103515625a(29) =12207031250