a(n) = 5*a(n-1) - 10*a(n-2), with a(0)=0, a(1)=1.

Terms

a(0) =0a(1) =1a(2) =5a(3) =15a(4) =25a(5) =-25a(6) =-375a(7) =-1625a(8) =-4375a(9) =-5625a(10) =15625a(11) =134375a(12) =515625a(13) =1234375a(14) =1015625a(15) =-7265625a(16) =-46484375a(17) =-159765625a(18) =-333984375a(19) =-72265625a(20) =2978515625a(21) =15615234375a(22) =48291015625a(23) =85302734375a(24) =-56396484375