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A276260
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Odd primes p such that p is in the trajectory of p+1 under the Collatz 3x+1 map (A014682).
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1
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OFFSET
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1,1
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COMMENTS
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LINKS
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MATHEMATICA
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Select[Prime@ Range[2, 10^5], MemberQ[NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, # + 1, # > 1 &], #] &] (* Michael De Vlieger, Aug 26 2016 *)
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PROG
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(JavaScript) function isit_collatz_prime(p)
{
var cur = p+1;
while(cur != p && cur != 2)
{
if(cur%2!=0)
{
cur = 3*cur + 1;
}else
{
cur = cur/2;
}
}
if(cur === p ){return "p is a Collatz prime"; }
else {return "p is not a Collatz prime"; }
}
(PARI) next_collatz_iteration(n) = if(n%2==1, return(3*n+1), return(n/2))
is(n) = if(n%2==1 && ispseudoprime(n), my(k=n+1); while(k > 1, k=next_collatz_iteration(k); if(k==n, return(1)))); 0 \\ Felix Fröhlich, Aug 26 2016
(PARI) has(n)=my(k=n+1); k>>=valuation(k, 2); while(k>1, k+=(k+1)>>1; k>>=valuation(k, 2); if(k==n, return(1))); 0
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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