A276260 Odd primes p such that p is in the trajectory of p+1 under the Collatz 3x+1 map (A014682).
5, 13, 17, 53, 61, 107, 251, 283, 1367
Offset: 1
Programs
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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";} } -
Mathematica
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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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
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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 forprime(p=3,1e9, if(has(p), print1(p", "))) \\ Charles R Greathouse IV, Aug 26 2016
Comments