连这也可以有通项公式的!
任取自然数 m,n, m≥n, 在集合 {0,1,2,...,n} 中,
有且仅有一个元素 k, 使得 \(\frac{(m+n-k)!}{k!(m-k)!(n-k)!}\) 为奇数。
记满足 \(\frac{(m+n-k)!}{k!(m-k)!(n-k)!}\) 为奇数的 k 为 a(m,n)=k,
a(0,0)=0,
a(1,0)=0, a(1,1)=1,
a(2,0)=0, a(2,1)=0, a(2,2)=2,
a(3,0)=0, a(3,1)=1, a(3,2)=2, a(3,3)=3,
a(4,0)=0, a(4,1)=0, a(4,2)=0, a(4,3)=0, a(4,4)=4,
00
00,01,
00,00,02,
00,01,02,03,
00,00,00,00,04,
00,01,00,01,04,05,
00,00,02,02,04,04,06,
00,01,02,03,04,05,06,07,
00,00,00,00,00,00,00,00,08,
00,01,00,01,00,01,00,01,08,09,
00,00,02,02,00,00,02,02,08,08,10,
00,01,02,03,00,01,02,03,08,09,10,11,
00,00,00,00,04,04,04,04,08,08,08,08,12,
00,01,00,01,04,05,04,05,08,09,08,09,12,13,
00,00,02,02,04,04,06,06,08,08,10,10,12,12,14,
00,01,02,03,04,05,06,07,08,09,10,11,12,13,14,15,
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,16,
00,01,00,01,00,01,00,01,00,01,00,01,00,01,00,01,16,17,
00,00,02,02,00,00,02,02,00,00,02,02,00,00,02,02,16,16,18,
00,01,02,03,00,01,02,03,00,01,02,03,00,01,02,03,16,17,18,19,
00,00,00,00,04,04,04,04,00,00,00,00,04,04,04,04,16,16,16,16,20,
00,0100,01,04,05,04,05,00,01,00,01,04,05,04,05,16,17,16,17,20,21,
00,00,02,02,04,04,06,06,00,00,02,02,04,04,06,06,16,16,18,18,20,20,22,
00,01,02,03,04,05,06,07,00,01,02,03,04,05,06,07,16,17,18,19,20,21,22,23,
00,00,00,00,00,00,00,00,08,08,08,08,08,08,08,08,16,16,16,16,16,16,16,16,24,
00,01,00,01,00,01,00,01,08,09,08,09,08,09,08,09,16,17,16,17,16,17,16,17,24,25,
00,00,02,02,00,00,02,02,08,08,10,10,08,08,10,10,16,16,18,18,16,16,18,18,24,24,26,
00,01,02,03,00,01,02,03,08,09,10,11,08,09,10,11,16,17,18,19,16,17,18,19,24,25,26,27,
00,00,00,00,04,04,04,04,08,08,08,08,12,12,12,12,16,16,16,16,20,20,20,20,24,24,24,24,28,
00,01,00,01,04,05,04,05,08,09,08,09,12,13,12,13,16,17,16,17,20,21,20,21,24,25,24,25,28,29,
00,00,02,02,04,04,06,06,08,08,10,10,12,12,14,14,16,16,18,18,20,20,22,22,24,24,26,26,28,28,30,
00,01,02,03,04,05,06,07,08,09,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,28,30,31, |