a(n) = (7*n^2-5*n+2)/2.

Terms

a(0) =1a(1) =2a(2) =10a(3) =25a(4) =47a(5) =76a(6) =112a(7) =155a(8) =205a(9) =262a(10) =326a(11) =397a(12) =475a(13) =560a(14) =652a(15) =751a(16) =857a(17) =970a(18) =1090a(19) =1217a(20) =1351a(21) =1492a(22) =1640a(23) =1795a(24) =1957a(25) =2126a(26) =2302a(27) =2485a(28) =2675a(29) =2872