a(n) = (5*n)^2.

Terms

a(0) =0a(1) =25a(2) =100a(3) =225a(4) =400a(5) =625a(6) =900a(7) =1225a(8) =1600a(9) =2025a(10) =2500a(11) =3025a(12) =3600a(13) =4225a(14) =4900a(15) =5625a(16) =6400a(17) =7225a(18) =8100a(19) =9025a(20) =10000a(21) =11025a(22) =12100a(23) =13225a(24) =14400a(25) =15625a(26) =16900a(27) =18225a(28) =19600a(29) =21025