A182262 Least prime p that 6^n - p is prime.

3, 5, 5, 5, 17, 7, 17, 7, 7, 7, 59, 19, 17, 13, 7, 19, 137, 13, 19, 7, 23, 97, 19, 89, 17, 223, 29, 109, 5, 19, 5, 59, 197, 5, 17, 307, 59, 83, 109, 157, 19, 23, 43, 109, 103, 7, 23, 19, 7, 269, 43, 13, 5, 67, 89, 83, 479, 53, 53, 383, 7, 83, 113, 37, 5, 23

Offset: 1

Author

Mateusz Szymański, Apr 21 2012

Keywords

• nonn

Examples

			For n=3 p=5 is the least prime that 6^3-p is prime (211).
		

Links

• Robert Israel, Table of n, a(n) for n = 1..2035

Crossrefs

Cf. A013607, A059614 (n such that a(n)=5).

Programs

Maple

f:= proc(n) local t,p;
  t:= 6^n;
  p:= 2;
  do
    p:= nextprime(p);
  until isprime(t-p);
  p
end proc:
map(f, [$1..100]); # Robert Israel, Nov 05 2020

Mathematica

f[n_] := Block[{p = 2}, While[! PrimeQ[6^n - p], p = NextPrime[p]];
  p]; Array[f, 60]

PARI

a(n) = my(p = 2); while(!isprime(6^n-p), p = nextprime(p+1)); p; \\ Michel Marcus, Mar 23 2016