OFFSET
1,2
MAPLE
A365228 := proc(n)
local j, k, s; s := 0;
for j from 1 to n do
for k from j to n do
if gcd(j, k) = 1 then s := s + 1/(j*k);
end if;
end do;
end do;
denom(s);
end proc;
seq(A365228(n), n = 1..30);
# second Maple program:
a:= n-> denom(add(add(`if`(igcd(j, k)=1, 1/j, 0), j=1..k)/k, k=1..n)):
seq(a(n), n=1..45); # Alois P. Heinz, Aug 28 2023
MATHEMATICA
a[n_Integer]:=Module[{sum, j, k}, sum=Sum[If[GCD[j, k]==1, 1/(j*k), 0], {j, 1, n}, {k, j, n}]; Denominator[sum]]; Table[a[n], {n, 1, 34}] (* Robert P. P. McKone, Aug 29 2023 *)
PROG
(PARI) a(n) = denominator(sum(j=1, n, sum(k=j, n, if (gcd(j, k)==1, 1/(j*k))))); \\ Michel Marcus, Aug 28 2023
(Python)
from fractions import Fraction
from math import gcd
def A365228(n): return sum(sum(Fraction(1, j) for j in range(1, k+1) if gcd(j, k)==1)/k for k in range(1, n+1)).denominator # Chai Wah Wu, Aug 29 2023
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Franz Vrabec, Aug 28 2023
STATUS
approved