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A053285 Totient of 2^n+1. 1
1, 2, 4, 6, 16, 20, 48, 84, 256, 324, 800, 1364, 3840, 5460, 12544, 19800, 65536, 87380, 186624, 349524, 986880, 1365336, 3345408, 5592404, 16515072, 20250000, 52306176, 84768120, 252645120, 351847488, 760320000, 1431655764, 4288266240 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 0..1062 (terms 0..300 from Robert Israel)

FORMULA

a(n) = A000010(A000051(n)).

EXAMPLE

It is a power of 2 iff n is a Fermat prime.

MAPLE

seq(numtheory:-phi(2^n+1), n=0..50); # Robert Israel, Aug 12 2015

MATHEMATICA

Table[EulerPhi[2^n + 1], {n, 35}] (* Vincenzo Librandi, Aug 12 2015 *)

PROG

(PARI) vector(40, n, eulerphi(2^n+1)) \\ Michel Marcus, Aug 12 2015

(MAGMA) [EulerPhi(2^n+1) : n in [1..40]]; // Vincenzo Librandi, Aug 12 2015

CROSSREFS

Cf. A000010, A000225, A051953, A000051.

Sequence in context: A067662 A248334 A001774 * A286850 A228119 A078148

Adjacent sequences:  A053282 A053283 A053284 * A053286 A053287 A053288

KEYWORD

nonn

AUTHOR

Labos Elemer, Mar 03 2000

EXTENSIONS

a(0)=1 prepended by Alois P. Heinz, Aug 12 2015

STATUS

approved

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Last modified September 20 00:58 EDT 2021. Contains 347577 sequences. (Running on oeis4.)