A061042 Denominator of 1/16 - 1/n^2.

1, 400, 144, 784, 64, 1296, 400, 1936, 18, 2704, 784, 3600, 256, 4624, 1296, 5776, 50, 7056, 1936, 8464, 576, 10000, 2704, 11664, 49, 13456, 3600, 15376, 1024, 17424, 4624, 19600, 81, 21904, 5776, 24336, 1600, 26896, 7056, 29584

Offset: 4

Author

N. J. A. Sloane, May 26 2001

Keywords

• nonn
• frac
• nice
• easy

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).

Crossrefs

See A061041 for comments, references, links.

Programs

Haskell

import Data.Ratio ((%), denominator)
a061042 n = denominator (1%16 - 1%n^2)  -- Reinhard Zumkeller, May 30 2012

Mathematica

Denominator/@(1/16-1/Range[4,50]^2) (* Harvey P. Dale, May 14 2011 *)

PARI

a(n)=denominator(1/16 - 1/n^2) \\ Charles R Greathouse IV, Feb 07 2017

Formula

a(n) = 16*n^2 / gcd(16*n^2, n^2-16). - Colin Barker, Jan 13 2014