OFFSET
1,2
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..1000
Amarnath Murthy, Some Notions on Least Common Multiples, Smarandache Notions Journal, Vol. 12, No. 1-2-3 (Spring 2001), pp. 307-308.
Index entries for linear recurrences with constant coefficients, signature (0,4,0,-6,0,4,0,-1).
FORMULA
G.f.: (x^4 + 2x^3 + 6x^2 + 2x + 1)/(1 - x^2)^4.
a(n) = binomial(n+2,3)*(3-(-1)^n)/4. - Gary Detlefs, Apr 13 2011
Quasipolynomial: a(n) = n(n+1)(n+2)/6 when n is odd and n(n+1)(n+2)/12 otherwise. - Charles R Greathouse IV, Feb 27 2012
a(n) = A033931(n) / 6. - Reinhard Zumkeller, Jul 04 2012
From Amiram Eldar, Sep 29 2022: (Start)
Sum_{n>=1} 1/a(n) = 6*(1 - log(2)).
Sum_{n>=1} (-1)^(n+1)/a(n) = 6*(3*log(2) - 2). (End)
EXAMPLE
a(6) = 28 as lcm(6,7,8)/6 = 168/6 = 28.
MATHEMATICA
Table[LCM[n, n+1, n+2]/6, {n, 50}] (* Harvey P. Dale, Jan 11 2011 *)
PROG
(PARI) { for (n=1, 1000, write("b067046.txt", n, " ", lcm(lcm(n, n+1), n+2)/6) ) } \\ Harry J. Smith, Apr 30 2010
(PARI) a(n)=binomial(n+2, 3)/(2-n%2) \\ Charles R Greathouse IV, Feb 27 2012
(Haskell)
a067046 = (`div` 6) . a033931 -- Reinhard Zumkeller, Jul 04 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Amarnath Murthy, Dec 30 2001
STATUS
approved