a(n) = n*((4*n + 1)*(7*n - 4) + 15*n*(-1)^n)/48.

Terms

a(0) =0a(1) =5a(2) =11a(3) =39a(4) =60a(5) =130a(6) =175a(7) =306a(8) =384a(9) =595a(10) =715a(11) =1025a(12) =1196a(13) =1624a(14) =1855a(15) =2420a(16) =2720a(17) =3441a(18) =3819a(19) =4715a(20) =5180a(21) =6270a(22) =6831a(23) =8134a(24) =8800a(25) =10335a(26) =11115a(27) =12901a(28) =13804a(29) =15860