A088110 Numbers n such that 2^n + n and 2^n - n are noncomposite.

0, 1, 3, 9

Offset

1,3

Comments

Conjecture: sequence is finite.

No more terms < 88075. - David Wasserman, Jul 20 2005

Links

Table of n, a(n) for n=1..4.

Example

9 is a member as 2^9 + 9 = 521 and 2^9 - 9 = 503 are primes.

Mathematica

Join[{0, 1}, Select[Range[1000], PrimeQ[2^# + #] && PrimeQ[2^# -#] &]] (* Vincenzo Librandi, Dec 08 2015 *)

Prog

(Magma) [0, 1] cat [n: n in [0..1000] | IsPrime(2^n+n) and IsPrime(2^n-n)]; // Vincenzo Librandi, Dec 08 2015

Crossrefs

Cf. A048744, A052007.

Sequence in context: A278974 A063103 A058847 * A122759 A247042 A274400

Adjacent sequences: A088107 A088108 A088109 * A088111 A088112 A088113

Keyword

more,nonn

Author

Amarnath Murthy, Sep 25 2003

Status

approved