A061042 - OEIS

%I #19 Oct 09 2023 11:21:19

%S 1,400,144,784,64,1296,400,1936,18,2704,784,3600,256,4624,1296,5776,

%T 50,7056,1936,8464,576,10000,2704,11664,49,13456,3600,15376,1024,

%U 17424,4624,19600,81,21904,5776,24336,1600,26896,7056,29584

%N Denominator of 1/16 - 1/n^2.

%H Reinhard Zumkeller, <a href="/A061042/b061042.txt">Table of n, a(n) for n = 4..10000</a>

%H <a href="/index/Rec#order_72">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, -6, 0, 0, 0, 0, 0, 0, 0, 10, 0, 0, 0, 0, 0, 0, 0, -12, 0, 0, 0, 0, 0, 0, 0, 12, 0, 0, 0, 0, 0, 0, 0, -10, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 0, 0, -3, 0, 0, 0, 0, 0, 0, 0, 1).

%F a(n) = 16*n^2 / gcd(16*n^2, n^2-16). - _Colin Barker_, Jan 13 2014

%t Denominator/@(1/16-1/Range[4,50]^2) (* _Harvey P. Dale_, May 14 2011 *)

%o (Haskell)

%o import Data.Ratio ((%), denominator)

%o a061042 n = denominator (1%16 - 1%n^2)  -- _Reinhard Zumkeller_, May 30 2012

%o (PARI) a(n)=denominator(1/16 - 1/n^2) \\ _Charles R Greathouse IV_, Feb 07 2017

%Y See A061041 for comments, references, links.

%K nonn,frac,nice,easy

%O 4,2

%A _N. J. A. Sloane_, May 26 2001