Talk:Giuga numbers: Difference between revisions
maybe?
(found PARI on mersenneforum.org/showthread.php?t=4666 . Extreme fast) |
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much faster.
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:: Presumably you meant <lang parigp>a(n)=print("n=",n);s=p=vector(n-2);t=p[1]=p[2]=2;s[1]=1/2;\
while(t>1,p[t]=nextprime(p[t]+1);s[t]=s[t-1]+1/p[t];\
if(s[t]==1||s[t]+(n-t)/p[t]<=1,t--,\
if(t<n-2,t++;p[t]=max(p[t-1],s[t-1]/(1-s[t-1])),\
c=numerator(s[n-2]);d=denominator(s[n-2]);k=d^2+c-d;f=divisors(k);\
for(i=1,(length(f)+1)\2,h=f[i];if((h+d)%(d-c)==0&&(k/h+d)%(d-c)==0,\
r1=(h+d)/(d-c);r2=(k/h+d)/(d-c);\
if(r1>p[n-2]&&r2>p[n-2]&&r1!=r2&&isprime(r1)&&isprime(r2),\
w=d*r1*r2;print(w);write("giuga.txt",w)))))))</lang>
::But I'm having problems reading that code. Specifically: <code>for(i=1,(length(f)+1)\2,h=f[i]</code> -- I haven't been able to find any documentation on what <code>\2</code> means in this context. Do you know where I should be looking? --[[User:Rdm|Rdm]] ([[User talk:Rdm|talk]]) 13:00, 14 July 2022 (UTC)
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