login
A176112
Primes that take a prime number of steps to reach 1 under the Collatz function.
2
3, 5, 41, 43, 53, 61, 109, 139, 149, 163, 167, 173, 179, 227, 233, 269, 307, 317, 373, 401, 439, 443, 479, 541, 557, 563, 607, 617, 619, 661, 751, 787, 827, 863, 911, 937, 1069, 1087, 1093, 1097, 1193, 1259, 1297, 1303, 1321, 1373, 1381, 1409, 1439
OFFSET
1,1
COMMENTS
Primes p such that A006577(p) is prime. - Charles R Greathouse IV, May 12 2015
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
MATHEMATICA
pnsQ[n_]:=PrimeQ[Length[NestWhileList[If[EvenQ[#], #/2, 3#+1]&, n, #>1&]]- 1]; Select[Prime[Range[500]], pnsQ] (* Harvey P. Dale, Nov 28 2016 *)
PROG
(PARI) A006577(n)=my(s); while(n>1, n=if(n%2, 3*n+1, n/2); s++); s
select(p->isprime(A006577(p)), primes(100)) \\ Charles R Greathouse IV, May 12 2015
CROSSREFS
Cf. A006577.
Sequence in context: A300938 A183258 A077779 * A215133 A146318 A228968
KEYWORD
nonn
AUTHOR
Kent Edward Hays (hayske(AT)gmail.com), Apr 08 2010
STATUS
approved