A116535 a(n) is the smallest odd prime p such that 2^n + p is not prime.

3, 7, 5, 7, 5, 3, 5, 5, 3, 3, 3, 3, 5, 3, 3, 5, 5, 3, 5, 3, 3, 3, 3, 3, 3, 3, 3, 3, 5, 3, 5, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 5, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 5, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 5, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3

Offset

0,1

Comments

The sequence is bounded, namely {a(n)} = {3, 5, 7}, because one of the numbers 2^n + 3, 2^n + 5, 2^n + 7 is divisible by 3. - Thomas Ordowski, Apr 11 2019

Links

Amiram Eldar, Table of n, a(n) for n = 0..10000

Example

A000079(20) + a(20) = 1048576 + 3 = 1048579 = 7*163*919.

Mathematica

Table[p := 2; While[PrimeQ[2^n + Prime[p]], p++ ]; Prime[p], {n, 0, 150}] (* Stefan Steinerberger, Mar 28 2006 *)

Crossrefs

Cf. A000079, A000040.

Sequence in context: A238048 A010624 A019638 * A287660 A122001 A161327

Adjacent sequences: A116532 A116533 A116534 * A116536 A116537 A116538

Keyword

nonn

Author

Reinhard Zumkeller, Mar 27 2006

Extensions

More terms from Stefan Steinerberger, Mar 28 2006

Status

approved