190103

Ruby


A320843(1)

出力してみた。

def search(a, num, n)
  if num == n + 1
    @cnt += 1
  else
    (1..n).each{|i|
      if a[i] == 0
        if num % i == 0 || i % num == 0
          a[i] = num
          search(a, num + 1, n)
          a[i] = 0
        end
      end
    }
  end
end

def A(n)
  a = [0] * (n + 1)
  @cnt = 0
  search(a, 1, n)
  @cnt
end

p (0..20).map{|i| A(i)}

出力結果
 [1, 1, 2, 3, 8, 10, 36, 41, 132, 250, 700, 750, 4010, 4237, 10680, 24679, 87328, 90478, 435812, 449586, 1939684]