OFFSET
0,3
COMMENTS
LINKS
Harry J. Smith, Table of n, a(n) for n = 0..400
Index entries for linear recurrences with constant coefficients, signature (0, 0, 3).
FORMULA
a(n) = 4*3^floor(n/3), n >= 3. - Vladeta Jovovic, Jul 18 2001
G.f.: (1+x+2*x^2+3*x^3+9*x^4+6*x^5+18*x^6)/(1-3*x^3).
EXAMPLE
a(4)=12 because a(4) is the LCM of 1,1,2,3,4 - which is clearly 12.
MATHEMATICA
Module[{nn=50, trms}, trms=CoefficientList[Series[(1+x+2x^2+x^4)/(1-3x^3), {x, 0, nn}], x]; Table[LCM@@Take[trms, n], {n, nn}]] (* or *) LinearRecurrence[{0, 0, 3}, {1, 1, 2, 6, 12, 12, 36}, 50] (* Harvey P. Dale, Oct 04 2024 *)
PROG
(PARI) a(n)=if(n<0, 0, if(n<4, n!, 4*3^(n\3)))
(Haskell)
a062723 n = a062723_list !! n
a062723_list = scanl1 lcm a000792_list
-- Reinhard Zumkeller, Dec 17 2011
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Felix Goldberg (felixg(AT)tx.technion.ac.il), Jul 15 2001
EXTENSIONS
Formula and correction from Vladeta Jovovic, Jul 18 2001
More terms from Jason Earls, Jul 21 2001
STATUS
approved