login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A052007
Numbers m such that 2^m + m is prime.
14
1, 3, 5, 9, 15, 39, 75, 81, 89, 317, 701, 735, 1311, 1881, 3201, 3225, 11795, 88071, 204129, 678561
OFFSET
1,2
COMMENTS
Terms >= 701 are currently only strong pseudoprimes.
If m=1 (mod 6) or m=2 (mod 6) then 3 divides 2^m+m. Thus for n > 1, a(n)!=1 (mod 6) and a(n)!=2 (mod 6).
Some of the results were computed using the PrimeFormGW (PFGW) primality-testing program. - Hugo Pfoertner, Nov 14 2019
Keller (see Links) notes that a Mersenne number M(2^m+m) = 2^(2^m+m) - 1 can be written as (2^m)*2^(2^m) - 1, and lists the first twelve terms of this sequence. The last known case where M(2^m+m) is prime is for m=a(4)=9, which gives the prime M(521). - Jeppe Stig Nielsen, Apr 20 2021
LINKS
W. Keller, New Cullen Primes, Math. Comp. 64 (1995), 1733-1741, S39.
Henri Lifchitz, Renaud Lifchitz, PRP Top Records. 2^n+n.
EXAMPLE
2^39 + 39 = 549755813927 is prime.
MATHEMATICA
Do[ If[ PrimeQ[ 2^n + n ], Print[ n ] ], {n, 0, 7000} ]
v={1}; Do[If[Mod[n, 2]*(Mod[n, 6]-1)!= 0&&PrimeQ[2^n+n], v=Append[v, n]; Print[v]], {n, 2, 20000}]
PROG
(PARI) is(n)=isprime(2^n+n) \\ Charles R Greathouse IV, Feb 09 2017
CROSSREFS
KEYWORD
nonn,nice,hard,more
AUTHOR
EXTENSIONS
11795 from Farideh Firoozbakht, Aug 21 2003
88071 from Hugo Pfoertner, Dec 26 2004
More terms from Henri Lifchitz submitted by Ray Chandler, Mar 02 2007
STATUS
approved