16

def f(n):
  if n <= 1:
    return 0
  if n > 1 and n % 2 != 0:
    return f(n-1) + 3 * n ** 2
  if n > 1 and n % 2 == 0:
    return n // 2 + f(n-1) + 2

print( f(49) )