OFFSET
1,2
LINKS
Robert Israel, Table of n, a(n) for n = 1..3952
EXAMPLE
3 is in the sequence because 1/1^4 +1/2^4 + 1/3^4 = 1393/1296 and 1/1^2 + 1/2^2 + 1/3^2 = 49/36, and 1296/36 = 36 = 6^2.
MAPLE
dd:= (n, s) -> denom(add(1/k^s, k=1..n)):
select(t -> issqr(dd(t, 4)/dd(t, 2)), [$1..1000]); # Robert Israel, May 18 2014
PROG
(PARI) default(realprecision, 1000); for(n=1, 300, if(sqrt(denominator(sum(i=1, n, 1/i^4))/denominator(sum(i=1, n, 1/i^2))) == floor(sqrt(denominator(sum(i=1, n, 1/i^4))/denominator(sum(i=1, n, 1/i^2)))), print1(n, ", ")))
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 07 2002
STATUS
approved