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 A276260 Odd primes p such that p is in the trajectory of p+1 under the Collatz 3x+1 map (A014682). 1
 5, 13, 17, 53, 61, 107, 251, 283, 1367 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(10) > 10^7 if it exists. - Felix Fröhlich, Aug 26 2016 a(10) > 10^9 if it exists. - Charles R Greathouse IV, Aug 26 2016 a(10) > 10^12 if it exists. - Charles R Greathouse IV, Sep 07 2016 LINKS Table of n, a(n) for n=1..9. Index entries for sequences related to 3x+1 (or Collatz) problem MATHEMATICA Select[Prime@ Range[2, 10^5], MemberQ[NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, # + 1, # > 1 &], #] &] (* Michael De Vlieger, Aug 26 2016 *) PROG (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 forprime(p=3, 1e9, if(has(p), print1(p", "))) \\ Charles R Greathouse IV, Aug 26 2016 CROSSREFS Cf. A014682, A276290. Sequence in context: A087484 A019382 A330732 * A350379 A145040 A361563 Adjacent sequences: A276257 A276258 A276259 * A276261 A276262 A276263 KEYWORD nonn,more AUTHOR Marina Ibrishimova, Aug 26 2016 STATUS approved

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Last modified December 11 13:16 EST 2023. Contains 367727 sequences. (Running on oeis4.)