OFFSET
0,6
EXAMPLE
a(0)=0 because 2^0+3^0=1+1=2 is prime,
a(3)=1 because 2^3+3^1=8+3=11 is prime,
a(17)=8 because 2^17+3^8=131072+6561=137633 is prime,
a(25)=27 because 33554432+7625597484987=7625631039419 is prime, etc.
MATHEMATICA
a[n_] := Module[{m, t = 2^n}, For[m = 0, True, m++, If[PrimeQ[t + 3^m], Return[m]]]];
Table[a[n], {n, 0, 100}] (* Jean-François Alcover, Feb 01 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Oct 11 2006
STATUS
approved