OFFSET
1,6
COMMENTS
k needs to be checked only up through n^2+1 since beyond this n^2 < (n*k)^2/(k^2 - n^2) < n^2 + 1 and thus can't be an integer. - Micah Manary, Aug 27 2022
LINKS
Micah Manary, Table of n, a(n) for n = 1..1000
PROG
(PARI) a(n) = sum(k=1, n^2+1, if (k!=n, denominator((n*k)^2/(k^2 - n^2))==1)); \\ Michel Marcus, Oct 28 2022
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Ctibor O. Zizka, Dec 06 2008
EXTENSIONS
More terms from Micah Manary, Aug 07 2022
STATUS
approved