a(n) = Sum_{-n <= a, b, c <= n} (b^2 - 4*a*c).

Terms

a(0) =18a(1) =250a(2) =1372a(3) =4860a(4) =13310a(5) =30758a(6) =63000a(7) =117912a(8) =205770a(9) =339570a(10) =535348a(11) =812500a(12) =1194102a(13) =1707230a(14) =2383280a(15) =3258288a(16) =4373250a(17) =5774442a(18) =7513740a(19) =9648940a(20) =12244078a(21) =15369750a(22) =19103432a(23) =23529800a(24) =28741050a(25) =34837218a(26) =41926500a(27) =50125572a(28) =59559910a(29) =70364110