The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A271842 Positive numbers n such that n^2 - 1 divides 4^n - 1. 3
 2, 4, 6, 16, 36, 52, 66, 256, 378, 456, 1296, 1470, 1548, 1800, 2002, 2556, 4356, 6480, 8008, 11952, 23580, 26320, 33930, 36636, 37170, 43290, 44100, 47520, 47880, 49680, 57240, 65536, 74448, 84420, 97812, 101920, 127050, 134946, 139860, 141156, 157080, 164880, 165600, 209220, 225456 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..1000 EXAMPLE 2 is in this sequence because (4^2 - 1)/(2^2 - 1) = 5. MAPLE A271842:=n->`if`((4^n-1) mod (n^2-1) = 0, n, NULL): seq(A271842(n), n=2..10^4); # Wesley Ivan Hurt, Apr 18 2016 MATHEMATICA Select[Range[1, 100], IntegerQ[(4^# - 1)/(#^2 - 1)] &] (* G. C. Greubel, Apr 15 2016 *) PROG (Magma) [0] cat [n: n in [2..240000] | Denominator((4^n-1)/(n^2-1)) eq 1]; (PARI) is(n)=Mod(4, n^2-1)^n==1 \\ Charles R Greathouse IV, Apr 15 2016 CROSSREFS Cf. positive numbers n such that n^2 - 1 divides (2^k)^n - 1: A247219 (k=1), this sequence (k=2), A242062 (k=3). Sequence in context: A167569 A032503 A050838 * A261864 A071243 A112086 Adjacent sequences: A271839 A271840 A271841 * A271843 A271844 A271845 KEYWORD nonn AUTHOR Juri-Stepan Gerasimov, Apr 15 2016 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 22 19:53 EST 2024. Contains 370260 sequences. (Running on oeis4.)