a(n) = n * (2*n + 1) * (6*n^2 + 4*n + 1) / 3.

Terms

a(0) =0a(1) =11a(2) =110a(3) =469a(4) =1356a(5) =3135a(6) =6266a(7) =11305a(8) =18904a(9) =29811a(10) =44870a(11) =65021a(12) =91300a(13) =124839a(14) =166866a(15) =218705a(16) =281776a(17) =357595a(18) =447774a(19) =554021a(20) =678140a(21) =822031a(22) =987690a(23) =1177209a(24) =1392776a(25) =1636675a(26) =1911286a(27) =2219085a(28) =2562644a(29) =2944631