This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
Do[f=(2^n+3^n)/5; If[PrimeQ[f], Print[{n, f}]], {n, 1, 1000}]
Select[Table[(3^n+2^n)/5,{n,500}],PrimeQ] (* Harvey P. Dale, Aug 07 2019 *)
is(n)=ispseudoprime((48^n+47^n)/95) \\ Charles R Greathouse IV, Jun 13 2017
is(n)=ispseudoprime((138^n+137^n)/275) \\ Charles R Greathouse IV, Jun 13 2017
is(n)=ispseudoprime((140^n+139^n)/279) \\ Charles R Greathouse IV, Jun 13 2017
a(10) = 4 because (5^29 + 4^29)/9 = 2149818248341 is prime and (2^29 + 1^29)/3, (3^29 + 2^29)/5 and (4^29 + 3^29)/7 are all composite.
Table[p = Prime[n]; k = 1; While[q = ((b+1)^n+b^n)/(2*b+1); ! PrimeQ[q], k++]; k, {n, 200}]
f[n_] := Block[{b = 1, p = Prime@ n}, While[! PrimeQ[((b +1)^p + b^p)/(2b +1)], b++]; b]; Array[f, 70, 2] (* Robert G. Wilson v, Jun 13 2018 *)
for(n=2, 200, b=0; until(isprime((((b+1)^prime(n)+b^prime(n))/(2*b+1))), b++); print1(b,", ")) \\ corrected by Eric Chen, Jun 06 2018
4 is in this sequence because (3^4 - (-2)^4)/5 = 13 is prime.
[n: n in [1..1000] | IsPrimePower((3^n-(-2)^n) div 5)];
Select[Range[2000], PrimeQ[(3^# - (-2)^#)/5] &] (* Michael De Vlieger, Dec 09 2017 *)
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