Sum[Floor[(a*i^2+b*i+c)/m], {i, 1, n}] in closed algebraic form and output.

def sum_floor_quadratic(a,b,c,m,n):
    return n/2*m + n/2*(a*n*n + b*n + c - m) + (1/2*(n%2) + 1/2)*(a*(n%2)**2 + b*(n%2) + c - m)
    
sum_floor_quadratic(1,2,3,4,5)