OFFSET
1,1
FORMULA
a(n) = lcm(n^2, 2).
From R. J. Mathar, Mar 06 2008: (Start)
O.g.f.: -2x(1 + 6x^2 + x^4 + 2x^3 + 2x)/((-1+x)^3 * (x+1)^3).
a(2n) = A016742(n).
a(2n+1) = A077591(n). (End)
a(n) = n*A109043(n). - Michel Marcus, Mar 13 2018
From Amiram Eldar, Jul 06 2022: (Start)
Sum_{n>=1} 1/a(n) = 5*Pi^2/48.
Sum_{n>=1} (-1)^(n+1)/a(n) = Pi^2/48 = -A245058. (End)
MATHEMATICA
LCM[Range[60]^2, 2] (* Harvey P. Dale, Jun 06 2018 *)
PROG
(PARI) a(n) = lcm(n^2, 2); \\ Michel Marcus, Mar 13 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
William A. Tedeschi, Feb 29 2008
STATUS
approved