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A027742
a(n) = phi(4^n-1)/(2*n).
0
1, 2, 6, 16, 60, 144, 756, 2048, 7776, 24000, 120032, 276480, 1719900, 4741632, 17820000, 67108864, 336849900, 725594112, 4822382628, 11842560000, 57802864896, 200778006528, 998132265920, 2283043553280, 13122000000000, 44980696051200, 178118842613760
OFFSET
1,2
MATHEMATICA
Table[EulerPhi[4^n-1]/(2n), {n, 30}] (* Harvey P. Dale, May 01 2013 *)
PROG
(PARI) a(n) = eulerphi(4^n-1)/(2*n) \\ Felix Fröhlich, Dec 02 2019
CROSSREFS
Sequence in context: A073959 A006820 A131385 * A324062 A033301 A197102
KEYWORD
nonn
AUTHOR
EXTENSIONS
Offset corrected by Sean A. Irvine, Dec 02 2019
STATUS
approved