On May 2, 2008, at 3:45 PM, William Stein wrote:

> The complexity mostly depends on the precision one uses in
> computing a certain Euler product approximation to zeta
> and also the number of factors in the product.  If you look
> at the PARI source code the comments do *not* inspire confidence in
> its correctness.  I had a student give a provable bound on precision
> and number of factors needed and wasn't able to get anything
> as good as what PARI uses.
>
> Here's the funny part of the PARI code (in trans3.c):
>
>   /* 1.712086 = ??? */
>   t = log( gtodouble(d) ) + (n + 0.5) * log(n) - n*(1+log2PI) +  
> 1.712086;

One way to check it is to use the bernoulli_mod_p_single() function,  
which computes B_k mod p for a single p and k, and uses a completely  
independent algorithm.

sage: x = bernoulli(240000)

sage: p = next_prime(500000)
sage: bernoulli_mod_p_single(p, 240000)
498812
sage: x % p
498812

sage: p = next_prime(10^6)
sage: bernoulli_mod_p_single(p, 240000)
841174
sage: x % p
841174

So I would say the answer is correct.

david


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