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
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
KEYWORD
nonn,more
AUTHOR
Marina Ibrishimova, Aug 26 2016
STATUS
approved