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

Terms

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