a(n) = n*(2*n^2 + 5*n + 1)/2.

Terms

a(0) =4a(1) =19a(2) =51a(3) =106a(4) =190a(5) =309a(6) =469a(7) =676a(8) =936a(9) =1255a(10) =1639a(11) =2094a(12) =2626a(13) =3241a(14) =3945a(15) =4744a(16) =5644a(17) =6651a(18) =7771a(19) =9010a(20) =10374a(21) =11869a(22) =13501a(23) =15276a(24) =17200a(25) =19279a(26) =21519a(27) =23926a(28) =26506a(29) =29265