A053286 Cototient of 2^n + 1.

1, 1, 1, 3, 1, 13, 17, 45, 1, 189, 225, 685, 257, 2733, 3841, 12969, 1, 43693, 75521, 174765, 61697, 731817, 848897, 2796205, 262145, 13304433, 14802689, 49449609, 15790337, 185023425, 313421825, 715827885, 6701057, 2957312961, 3551128577

Offset

0,4

Links

Amiram Eldar, Table of n, a(n) for n = 0..1122 (terms 1..250 from G. C. Greubel)

Formula

a(n) = A051953(A000051(n)).

Mathematica

Table[2^n + 1 - EulerPhi[2^n + 1], {n, 0, 50}] (* G. C. Greubel, May 31 2018 *)

Prog

(PARI) a(n) = my(x=2^n+1); x - eulerphi(x); \\ Michel Marcus, Aug 17 2017

Crossrefs

Cf. A000010, A000051, A000225, A051953.

Sequence in context: A133177 A184828 A331998 * A008826 A103440 A116483

Adjacent sequences: A053283 A053284 A053285 * A053287 A053288 A053289

Keyword

nonn

Author

Labos Elemer, Mar 03 2000

Extensions

Offset changed to 0 and a(0) prepended by Amiram Eldar, Jan 11 2024

Status

approved