A127908 Primes of form (3^n + 2^n)/5.

7, 463, 35839, 798167678837469920188160718521149336927, 24665899002341798194980052306171212216360861465143461865961807325057879, 5001149050738853423183653309332375420192266379562546200601855155172715420590196078603421469034502777938287

Offset: 1

Author

Alexander Adamchuk, Feb 05 2007

Keywords

• nonn

Comments

Numbers n such that (2^n + 3^n)/5 is prime are listed in A057469 = {3, 7, 11, 83, 149, 223, 599, 647, 1373, 8423, ...}.

Crossrefs

Cf. A057469.

Programs

Mathematica

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 *)

Formula

a(n) = (2^A057469(n) + 3^A057469(n))/5.