A074949 Denominators of Sum_{k=1..n} 1/lcm(n,k).

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

Amiram Eldar, Table of n, a(n) for n = 1..2308

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

Adjacent sequences: A074946 A074947 A074948 * A074950 A074951 A074952

Keyword

easy,frac,nonn

Author

Benoit Cloitre, Oct 05 2002

Status

approved