def solve(): def p(i): return i * (3 * i - 1) / 2 j = 1 while True: j += 1 pj = p(j) for k in reversed(range(1, j)): pk = p(k) if is_pentagonal(pj - pk) and is_pentagonal(pj + pk): return int(pj - pk)
def solve(): # t(n) = n(n + 1) / 2 für n = 2n - 1 # = (2n - 1)(2n - 1 + 1) / 2 # = (2n - 1)(2n) / 2 # = n(2n - 1) # = h(n) # # Therefore t(n) is a subset of h(n) def h(n): return n * (2 * n - 1) # Start from 144 as the answer must be greater than h(143) i = 144 while True: formula = h(i) if is_pentagonal(formula): return formula i += 1