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Problem 591


Problem 591


Best Approximations by Quadratic Integers

Given a non-square integer d, any real x can be approximated arbitrarily close by quadratic integers a+bd, where a,b are integers. For example, the following inequalities approximate π with precision 1013:
437563619152026188084046055<π<72113331558221019836515172
We call BQAd(x,n) the quadratic integer closest to x with the absolute values of a,b not exceeding n.
We also define the integral part of a quadratic integer as Id(a+bd)=a.

You are given that:

  • BQA2(π,10)=622
  • BQA5(π,100)=26555
  • BQA7(π,106)=5603232117817
  • I2(BQA2(π,1013))=6188084046055

Find the sum of |Id(BQAd(π,1013))| for all non-square positive integers less than 100.


二次整数最佳逼近

给定一个非完全平方的整数d,任意实数x可以用所谓二次整数a+bd任意逼近,其中a,b均为整数。例如如下不等式能够以1013的精度逼近π
437563619152026188084046055<π<72113331558221019836515172
我们记a,b不超过n的所有二次整数中最接近x的为BQAd(x,n)
同时我们定义二次整数的“整数”部分为Id(a+bd)=a

已知:

  • BQA2(π,10)=622
  • BQA5(π,100)=26555
  • BQA7(π,106)=5603232117817
  • I2(BQA2(π,1013))=6188084046055

对于所有小于100的非完全平方整数d,求其对应的|Id(BQAd(π,1013))|之和。


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