login
A074949
Denominators of Sum_{k=1..n} 1/lcm(n,k).
5
1, 1, 6, 6, 60, 60, 140, 420, 2520, 2520, 27720, 27720, 360360, 360360, 72072, 360360, 12252240, 12252240, 77597520, 46558512, 25865840, 33256080, 118982864, 5354228880, 8923714800, 3824449200, 80313433200, 80313433200, 2329089562800
OFFSET
1,3
LINKS
EXAMPLE
1, 1, 5/6, 5/6, 37/60, 47/60, 69/140, 263/420, 1321/2520, 1429/2520, ...
MAPLE
A074949:=proc(n) local i: RETURN(denom(add(1/ilcm(n, i), i=1..n))): end; seq(A074949(n), n=1..30); # C. Ronaldo
MATHEMATICA
a[n_] := Denominator @ Sum[1/LCM[k, n], {k, 1, n}]; Array[a, 30] (* Amiram Eldar, Jan 31 2021 *)
PROG
(PARI) a(n)=denominator(sum(i=1, n, 1/lcm(n, i)))
CROSSREFS
Cf. A074947 (numerators).
Sequence in context: A084675 A075179 A321971 * A078290 A269888 A269767
KEYWORD
easy,frac,nonn
AUTHOR
Benoit Cloitre, Oct 05 2002
STATUS
approved