OFFSET
4,2
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 4..10000
Index entries for linear recurrences with constant coefficients, 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).
FORMULA
a(n) = 16*n^2 / gcd(16*n^2, n^2-16). - Colin Barker, Jan 13 2014
MATHEMATICA
Denominator/@(1/16-1/Range[4, 50]^2) (* Harvey P. Dale, May 14 2011 *)
PROG
(Haskell)
import Data.Ratio ((%), denominator)
a061042 n = denominator (1%16 - 1%n^2) -- Reinhard Zumkeller, May 30 2012
(PARI) a(n)=denominator(1/16 - 1/n^2) \\ Charles R Greathouse IV, Feb 07 2017
CROSSREFS
KEYWORD
nonn,frac,nice,easy
AUTHOR
N. J. A. Sloane, May 26 2001
STATUS
approved