a(n) = (10*n + 5)^2.

Terms

a(0) =25a(1) =225a(2) =625a(3) =1225a(4) =2025a(5) =3025a(6) =4225a(7) =5625a(8) =7225a(9) =9025a(10) =11025a(11) =13225a(12) =15625a(13) =18225a(14) =21025a(15) =24025a(16) =27225a(17) =30625a(18) =34225a(19) =38025a(20) =42025a(21) =46225a(22) =50625a(23) =55225a(24) =60025a(25) =65025a(26) =70225a(27) =75625a(28) =81225a(29) =87025