a(n) = n^2*(n*(4*n + 3) + 3*n*(-1)^n - 4)/96.

Terms

a(0) =0a(1) =1a(2) =3a(3) =14a(4) =25a(5) =66a(6) =98a(7) =200a(8) =270a(9) =475a(10) =605a(11) =966a(12) =1183a(13) =1764a(14) =2100a(15) =2976a(16) =3468a(17) =4725a(18) =5415a(19) =7150a(20) =8085a(21) =10406a(22) =11638a(23) =14664a(24) =16250a(25) =20111a(26) =22113a(27) =26950a(28) =29435a(29) =35400