OFFSET
0,2
COMMENTS
LINKS
Robert Israel, Table of n, a(n) for n = 0..340
FORMULA
a(n) = denominator(s(n)) with the rationals (in lowest terms) s(n) = 1 + 2*Sum_{k=1..n} 1/(4*k^4 + 1), n >= 0.
EXAMPLE
See A292227.
MAPLE
seq(denom(t), t=ListTools:-PartialSums([1, seq(2/(4*k^4+1), k=1..30)])); # Robert Israel, Oct 30 2017
MATHEMATICA
{1}~Join~Denominator[1 + 2 Accumulate[Array[1/(4 #^4 + 1) &, 19]]] (* Michael De Vlieger, Oct 30 2017 *)
PROG
(PARI) a(n) = denominator(1+2*sum(k=1, n, 1/(4*k^4 + 1))); \\ Michel Marcus, Oct 30 2017
CROSSREFS
KEYWORD
nonn,frac,easy
AUTHOR
Wolfdieter Lang, Oct 30 2017
STATUS
approved