A027742 - OEIS

%I #18 Nov 30 2024 06:27:15

%S 1,2,6,16,60,144,756,2048,7776,24000,120032,276480,1719900,4741632,

%T 17820000,67108864,336849900,725594112,4822382628,11842560000,

%U 57802864896,200778006528,998132265920,2283043553280,13122000000000,44980696051200,178118842613760

%N a(n) = phi(4^n-1)/(2*n).

%H Amiram Eldar, <a href="/A027742/b027742.txt">Table of n, a(n) for n = 1..1122</a>

%F a(n) = A295501(n)/(2*n) = A027695(n)/2. - _Amiram Eldar_, Nov 30 2024

%t Table[EulerPhi[4^n-1]/(2n),{n,30}] (* _Harvey P. Dale_, May 01 2013 *)

%o (PARI) a(n) = eulerphi(4^n-1)/(2*n) \\ _Felix Fröhlich_, Dec 02 2019

%Y Cf. A000010, A027695, A295501.

%K nonn

%O 1,2

%A _N. J. A. Sloane_

%E Offset corrected by _Sean A. Irvine_, Dec 02 2019