Calkin-Wilf sequence: Difference between revisions
Add PARI/GP implementation
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The element 83116/51639 is at position 123456789 in the sequence.</pre>
=={{header|PARI/GP}}==
{{trans|Mathematica_/_Wolfram_Language}}
<syntaxhighlight lang="PARI/GP">
\\ This function assumes the existence of a global variable 'an' for 'a[n]'
a(n) = if(n==1, 1, 1 / (2 * floor(an[n-1]) + 1 - an[n-1]));
\\ We will use a vector to hold the values and compute them iteratively to avoid stack overflow
an = vector(20);
an[1] = 1;
for(i=2, 20, an[i] = a(i));
\\ Now we print the vector
print(an);
\\ Initialize variables for the while loop
a = 1;
n = 1;
\\ Loop until the condition is met
while(a != 83116/51639,{
a = 1/(2 * floor(a) + 1 - a);
if(n>=123456789,print(n));
n++;
});
\\ Output the number of iterations needed to reach 83116/51639
print(n);
</syntaxhighlight>
{{out}}
<pre>
[1, 1/2, 2, 1/3, 3/2, 2/3, 3, 1/4, 4/3, 3/5, 5/2, 2/5, 5/3, 3/4, 4, 1/5, 5/4, 4/7, 7/3, 3/8]
123456789
</pre>
=={{header|Pascal}}==
These programs were written in Free Pascal, using the Lazarus IDE and the Free Pascal compiler version 3.2.0. They are based on the Wikipedia article "Calkin-Wilf tree", rather than the algorithms in the task description.
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