A051426 Least common multiple of {2, 4, 6, ..., 2n}.

2, 4, 12, 24, 120, 120, 840, 1680, 5040, 5040, 55440, 55440, 720720, 720720, 720720, 1441440, 24504480, 24504480, 465585120, 465585120, 465585120, 465585120, 10708457760, 10708457760, 53542288800, 53542288800, 160626866400, 160626866400, 4658179125600

Offset

1,1

Comments

Gcd(A025547(n), a(n)) = A025547(floor((n+1)/2)). - Reinhard Zumkeller, Apr 25 2011

References

A. Murthy, Some new Smarandache sequences, functions and partitions, Smarandache Notions Journal Vol. 11 N. 1-2-3 Spring 2000 (but beware errors).

Links

T. D. Noe, Table of n, a(n) for n = 1..500

Index entries for sequences related to lcm's

Formula

a(n) = a(n-1)*lcm(a(n-1),2n) = a(n-1)* A014963(n). - Zak Seidov, Aug 01 2009

Example

a(3) = lcm{2,4,6} = 12;
a(7) = lcm{2,4,6,8,10,12,14} = 840.

Mathematica

SZ={2}; n=2; L=2; Do[L=LCM[L, 2n]; AppendTo[SZ, L]; n++, {99}]; SZ (* Zak Seidov, Aug 01 2009 *)
Table[LCM@@Range[2, 2n, 2], {n, 30}] (* Harvey P. Dale, Oct 09 2011 *)

Prog

(Haskell)
a051426 n = foldl lcm 1 [2, 4..2*n] -- Reinhard Zumkeller, Apr 25 2011
(PARI) a(n)=2*lcm([1..n]) \\ Charles R Greathouse IV, Oct 28 2016

Crossrefs

Cf. A003418, A025547.

Sequence in context: A096421 A066843 A051905 * A048148 A080375 A136253

Adjacent sequences: A051423 A051424 A051425 * A051427 A051428 A051429

Keyword

easy,nice,nonn

Author

Asher Auel

Extensions

a(6), a(7) and a(8) corrected by T. D. Noe, Feb 08 2008

Corrected the example, which did not reflect the sequence values provided. - Michael Davies (mykdavies+oeis(AT)gmail.com), Oct 10 2008

Edited by N. J. A. Sloane, Jul 31 2009 at the suggestion of R. J. Mathar

Status

approved