A069060 - OEIS

%I #17 Mar 05 2020 14:51:14

%S 3,5,27,17,1089,4225,16641,257,69257922561,1076890625,4198401,

%T 16785409,67125249,72075187834650625,1238166730171084290520186881,

%U 65537,17180131329,22301425772351053845871360015696103812890625,274878955521

%N Product of divisors of 2^n + 1.

%H Harvey P. Dale, <a href="/A069060/b069060.txt">Table of n, a(n) for n = 1..69</a>

%F a(n) = Product_{d|2^n + 1} d. - _Wesley Ivan Hurt_, Jan 23 2017

%F a(n) = A007955(A000051(n)). - _Michel Marcus_, Jan 24 2017

%t Times@@Divisors[#]&/@(2^Range[20]+1) (* _Harvey P. Dale_, Mar 05 2020 *)

%o (PARI) a(n) = my(d=divisors(2^n+1)); prod(k=1, #d, d[k]); \\ _Michel Marcus_, Jan 24 2017

%Y Cf. A000051, A007955.

%K easy,nonn

%O 1,1

%A _Benoit Cloitre_, Apr 04 2002