a(n) = (n+1)*(n^3+15*n^2+74*n+132)/12.

Terms

a(0) =11a(1) =37a(2) =87a(3) =172a(4) =305a(5) =501a(6) =777a(7) =1152a(8) =1647a(9) =2285a(10) =3091a(11) =4092a(12) =5317a(13) =6797a(14) =8565a(15) =10656a(16) =13107a(17) =15957a(18) =19247a(19) =23020a(20) =27321a(21) =32197a(22) =37697a(23) =43872a(24) =50775a(25) =58461a(26) =66987a(27) =76412a(28) =86797a(29) =98205