Thứ sáu ngày 13 dưới góc nhìn toán học và văn hóa
một số nước phương Tây, người ta cho rằng thứ sáu ngày 13 là ngày rủi ro. Vậy thứ sáu ngày 13 có đặc điểm gì về mặt toán học và văn hóa? Nó là ngày tốt hay xấu?Bằng lý thuyết đồng dư, toán học chứng minh được một năm bất kỳ có ít nhất một thứ sáu ngày 13 và nhiều nhất ba thứ sáu ngày 13. Hơn nữa, một năm có ba thứ sáu ngày 13 khi và chỉ khi ngày đầu năm là thứ năm (đối với năm không nhuận) hoặc chủ nhật (đối với năm nhuận).
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