Yellowstone sequence: Difference between revisions
Add PARI/GP implementation
imported>Maxima enthusiast No edit summary |
(Add PARI/GP implementation) |
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<pre> 1 2 3 4 9 8 15 14 5 6 25 12 35 16 7 10 21 20 27 22 39 11 13 33 26 45 28 51 32 17</pre>
=={{header|PARI/GP}}==
<syntaxhighlight lang="PARI/GP">
yellowstone(n) = {
my(a=3, o=2, u=[]);
if(n<3, return(n)); \\ Base case: return n if it is less than 3
print1("1, 2"); \\ Print initial values
for(i = 4, n, \\ Iterate from 4 to n
print1(", "a); \\ Print current value of a
u = setunion(u, Set(a)); \\ Add a to the set u
\\ Remove consecutive elements from u
while(#u > 1 && u[2] == u[1] + 1,
u = vecextract(u, "^1")
);
\\ Find next value of a
for(k = u[1] + 1, 1e10,
if(gcd(k, o) <= 1, next); \\ Skip if gcd(k, o) is greater than 1
if(setsearch(u, k), next); \\ Skip if k is in set u
if(gcd(k, a) != 1, next); \\ Skip if gcd(k, a) is not 1
o = a; \\ Update o to current a
a = k; \\ Update a to k
break
)
);
a \\ Return the final value of a
}
yellowstone(20); \\ Call the function with n = 20
</syntaxhighlight>
{{out}}
<pre>
1, 2, 3, 4, 9, 8, 15, 14, 5, 6, 25, 12, 35, 16, 7, 10, 21, 20, 27
</pre>
=={{header|Perl}}==
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