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本帖最后由 天山草 于 2023-11-28 10:42 编辑
已知数列 c(n) 的首项为 c(1) = 5/3; c(n+1) = a(n+2)/b(n+1);
a(0)=1; a(n)=a(n-1)+2; b(0)=1; b(n)=b(n-1)+1;
求 s(21)=c(1)+c(2)+c(3)+...+c(21) 化为最简分数的准确值。
- a[0] = 1; a[n_] := a[n] = (a[n - 1] + 2);
- b[0] = 1; b[n_] := b[n] = (b[n - 1] + 1);
- c[n_] := c[n] = (a[n] + 2)/(b[n] + 1);
- s[0] = 0; s[n_] := s[n] = (s[n - 1] + c[n]);
- Do[ Print["b(", n, ") = ", b[n], ", a(", n, ") = ", a[n], ", c(", n, ") = ", c[n], ", s(", n, ") = ", s[n]], {n, 1, 21}];
复制代码
运行结果:
b(1) = 2, a(1) = 3, c(1) = 5/3, s(1) = 5/3
b(2) = 3, a(2) = 5, c(2) = 7/4, s(2) = 41/12
b(3) = 4, a(3) = 7, c(3) = 9/5, s(3) = 313/60
b(4) = 5, a(4) = 9, c(4) = 11/6, s(4) = 141/20
b(5) = 6, a(5) = 11, c(5) = 13/7, s(5) = 1247/140
b(6) = 7, a(6) = 13, c(6) = 15/8, s(6) = 3019/280
b(7) = 8, a(7) = 15, c(7) = 17/9, s(7) = 31931/2520
b(8) = 9, a(8) = 17, c(8) = 19/10, s(8) = 36719/2520
b(9) = 10, a(9) = 19, c(9) = 21/11, s(9) = 456829/27720
b(10) = 11, a(10) = 21, c(10) = 23/12, s(10) = 509959/27720
b(11) = 12, a(11) = 23, c(11) = 25/13, s(11) = 7322467/360360
b(12) = 13, a(12) = 25, c(12) = 27/14, s(12) = 8017447/360360
b(13) = 14, a(13) = 27, c(13) = 29/15, s(13) = 8714143/360360
b(14) = 15, a(14) = 29, c(14) = 31/16, s(14) = 18824681/720720
b(15) = 16, a(15) = 31, c(15) = 33/17, s(15) = 343803337/12252240
b(16) = 17, a(16) = 33, c(16) = 35/18, s(16) = 122542379/4084080
b(17) = 18, a(17) = 35, c(17) = 37/19, s(17) = 2479416161/77597520
b(18) = 19, a(18) = 37, c(18) = 39/20, s(18) = 526146265/15519504
b(19) = 20, a(19) = 39, c(19) = 41/21, s(19) = 185482083/5173168
b(20) = 21, a(20) = 41, c(20) = 43/22, s(20) = 195593275/5173168
b(21) = 22, a(21) = 43, c(21) = 45/23, s(21) = 4731437885/118982864 |
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