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

Terms

a(0) =1a(1) =11a(2) =45a(3) =119a(4) =249a(5) =451a(6) =741a(7) =1135a(8) =1649a(9) =2299a(10) =3101a(11) =4071a(12) =5225a(13) =6579a(14) =8149a(15) =9951a(16) =12001a(17) =14315a(18) =16909a(19) =19799a(20) =23001a(21) =26531a(22) =30405a(23) =34639a(24) =39249a(25) =44251a(26) =49661a(27) =55495a(28) =61769a(29) =68499