a(n) = Sum_{i=1..n} (3i)^2.

Terms

a(0) =0a(1) =9a(2) =45a(3) =126a(4) =270a(5) =495a(6) =819a(7) =1260a(8) =1836a(9) =2565a(10) =3465a(11) =4554a(12) =5850a(13) =7371a(14) =9135a(15) =11160a(16) =13464a(17) =16065a(18) =18981a(19) =22230a(20) =25830a(21) =29799a(22) =34155a(23) =38916a(24) =44100a(25) =49725a(26) =55809a(27) =62370a(28) =69426a(29) =76995