A066903 Primes in A006577.

7, 2, 5, 3, 19, 17, 17, 7, 7, 23, 5, 13, 13, 109, 29, 11, 11, 11, 19, 19, 19, 19, 107, 107, 17, 17, 17, 17, 113, 113, 113, 7, 41, 41, 103, 103, 23, 23, 23, 23, 23, 23, 23, 67, 31, 31, 31, 31, 31, 31, 13, 13, 13, 13, 101, 101, 13, 13, 127, 83, 127, 47, 47, 109, 47, 109, 109

Offset: 1

Author

K. B. Subramaniam (kb_subramaniambalu(AT)yahoo.com), Dec 20 2001

Keywords

• nonn
• look

Examples

			a(1) = 7 because the first prime in A006577 is A006577(3) = 7.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A006577.

Programs

Maple

N:= 1000; # to get the first N terms
Collatz:= proc(n) option remember;
if n::even then 1+Collatz(n/2)
else 1+Collatz(3*n+1)
fi
end proc;
Collatz(1):= 0;
count:= 0;
for i from 1 while count < N do
  x:= Collatz(i);
  if isprime(x) then count:= count+1; A[count]:= x fi;
od:
seq(A[i],i=1..N); # Robert Israel, Jun 01 2014

Mathematica

M = 100;
Collatz[n_] := Collatz[n] = If[EvenQ[n], 1+Collatz[n/2], 1+Collatz[3n+1]];
Collatz[1] = 0;
count = 0;
For[i = 1, count < M, i++, x = Collatz[i]; If[PrimeQ[x], count = count+1; a[count] = x]];
Array[a, M] (* Jean-François Alcover, Mar 26 2019, after Robert Israel *)

Extensions

More terms from Sascha Kurz, Mar 23 2002

Offset corrected by Robert Israel, Jun 01 2014