A025558 a(n) = (n/(n+1)) * lcm(1,2,...,n+1).

1, 4, 9, 48, 50, 360, 735, 2240, 2268, 25200, 25410, 332640, 334620, 336336, 675675, 11531520, 11571560, 220540320, 221152932, 221707200, 222211080, 5121436320, 5131136010, 25700298624, 25741485000, 77338861600, 77445096300, 2248776129600, 2251453244040

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Comments

a(n) = (1/1 + 1/3 + 1/6 + ... + 1/C(n+1,2))*lcm(1,3,6,...,binomial(n+1,2)) = 2n/(n+1) * lcm(1,3,6,...,binomial(n+1,2)).

a(n+1) = a(n) * ((n+1)^2)/(n * ((n+2)/p) ), where p = n+2 if n+2 is prime, p = q if n+2 = q^k (q is prime, k>1), or p = 1 if n+2 is not a prime or a prime power. - Scott C. Macfarlan (scottmacfarlan(AT)covance.com), Jan 08 2004

Crossrefs

Cf. A002944, A003418.

Programs

Maple

a:= n-> (n/(n+1)) * ilcm($1..n+1):
seq(a(n), n=1..29);  # Alois P. Heinz, Mar 07 2022

Mathematica

Table[n/(n+1) LCM@@Range[n+1],{n,30}]  (* Harvey P. Dale, Apr 02 2011 *)

PARI

a(n) = n*lcm([1..n+1])/(n+1); \\ Michel Marcus, Mar 07 2022

Formula

a(n) = n * A002944(n+1) = (n/(n+1)) * A003418(n+1).

Extensions

Entry revised by N. J. A. Sloane, Nov 12 2004