■ベキ和とオイラー・マクローリンの和公式(その7)

 オイラー・マクローリンの和公式を

  Σ1/k^4

について適用してみたい.

  f(x)=1/x^4     f^(5)(x)=−8!/6x^9

  f’(x)=−4/x^5     f^(6)(x)=9!/6x^10

  f”(x)=20/x^6     f^(7)(x)=−10!/6x^11

  f^(3)(x)=−120/x^7  f^(8)(x)=11!/6x^12

  f^(4)(x)=840/x^8   f^(9)(x)=−12!/x^13

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  Σ(1,n)1/k^4〜∫(1,n)1/x^4dx+(f(n)+f(1))/2+ΣB2k/(2k)!(f^(2k-1)(n)-f^(2k-1)(1))+R

  ∫(1,n)1/x^4dx=[-1/3x^3]=-1/3n^3+1/3

  (f(n)+f(1))/2=(1/n^4+1)/2

  (f'(n)-f'(1))/12=(-4/n^5+4)/12

  (f^(3)(n)-f^(3)(1))/720=(-120/n^7+120)/720

  (f^(5)(n)-f^(5)(1))/30240=(-6720/n^9+6720)/30240

  (f^(7)(n)-f^(7)(1))/1209600=(-604800/n^9+60480040)/1209600

  Σ1/k^4〜-1/3n^3+1/2n^4-1/3n^5+1/6n^7+・・・+1/3+1/2+1/3-1/12+R

−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

  1+1/2^4 =1.0625

  1+1/2^4+1/3^4 =1.07485

  1+1/2^4+1/3^4+1/4^4 =1.07875

  1+1/2^4+1/3^4+1/4^4+1/5^4 =1.08035

  1+1/2^4+1/3^4+1/4^4+1/5^4+1/6^4 =1.08112

  1+1/2^4+1/3^4+1/4^4+1/5^4+1/6^4+1/7^4 =1.05154

  1+1/2^4+1/3^4+1/4^4+1/5^4+1/6^4+1/7^4+1/8^4 =1.08178

  1+1/2^4+1/3^4+1/4^4+1/5^4+1/6^4+1/7^4+1/8^4+1/9^4 =1.08194

  1+1/2^4+1/3^4+1/4^4+1/5^4+1/6^4+1/7^4+1/8^4+1/9^4+1/10^4=1.08204

  π^4/90=1.08232

  1/3+1/2+1/3-1/12=1.08333

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