a(n) = n*(n+1)*(2*n+1)/6 - n*floor(n/2).

Terms

a(0) =1a(1) =3a(2) =11a(3) =22a(4) =45a(5) =73a(6) =119a(7) =172a(8) =249a(9) =335a(10) =451a(11) =578a(12) =741a(13) =917a(14) =1135a(15) =1368a(16) =1649a(17) =1947a(18) =2299a(19) =2670a(20) =3101a(21) =3553a(22) =4071a(23) =4612a(24) =5225a(25) =5863a(26) =6579a(27) =7322a(28) =8149a(29) =9005