a(n) = (1/3!)*(n^3 + 24*n^2 + 107*n + 90), compare A059604.

Terms

a(0) =15a(1) =37a(2) =68a(3) =109a(4) =161a(5) =225a(6) =302a(7) =393a(8) =499a(9) =621a(10) =760a(11) =917a(12) =1093a(13) =1289a(14) =1506a(15) =1745a(16) =2007a(17) =2293a(18) =2604a(19) =2941a(20) =3305a(21) =3697a(22) =4118a(23) =4569a(24) =5051a(25) =5565a(26) =6112a(27) =6693a(28) =7309a(29) =7961