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A014945 Numbers n such that n divides 4^n - 1. 19
1, 3, 9, 21, 27, 63, 81, 147, 171, 189, 243, 441, 513, 567, 657, 729, 903, 1029, 1197, 1323, 1539, 1701, 1971, 2187, 2667, 2709, 3087, 3249, 3591, 3969, 4599, 4617, 5103, 5913, 6321, 6561, 7077, 7203, 8001, 8127, 8379, 9261, 9747, 10773, 11907, 12483 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This sequence is closed under multiplication. - Charles R Greathouse IV, Nov 03 2016

LINKS

Table of n, a(n) for n=1..46.

FORMULA

a(n) = A014741(n+1)/2.

MATHEMATICA

Select[Range[12500], Divisible[4^#-1, #]&]  (* Harvey P. Dale, Mar 23 2011 *)

PROG

(PARI) is(n)=Mod(4, n)^n==1 \\ Charles R Greathouse IV, Nov 03 2016

CROSSREFS

Sequence in context: A044055 A029542 A014962 * A045590 A242740 A029536

Adjacent sequences:  A014942 A014943 A014944 * A014946 A014947 A014948

KEYWORD

nonn

AUTHOR

Olivier Gérard

EXTENSIONS

More terms and better description from Benoit Cloitre, Mar 05 2002

STATUS

approved

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Last modified October 20 23:39 EDT 2018. Contains 316405 sequences. (Running on oeis4.)