A124447 - OEIS

A124447

a(n) = lcm(A066840(n), A124440(n)).

0, 1, 2, 3, 21, 5, 30, 12, 140, 16, 120, 18, 399, 99, 322, 48, 900, 533, 630, 60, 480, 425, 1122, 72, 11781, 360, 11102, 126, 4515, 352, 2760, 192, 2000, 832, 5406, 162, 9405, 2349, 6726, 240, 12810, 2046, 7392, 330, 27202, 4235, 9660, 288, 66306, 11656

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

LINKS

Table of n, a(n) for n=1..50.

EXAMPLE

Those positive integers which are coprime to 8 and are <= 8/2, are 1 and 3. Those integers which are coprime to 8 and are between 8/2 and 8, are 5 and 7.

So a(8) = lcm(1+3,5+7) = lcm(4,12) = 12.

MATHEMATICA

f1[n_] := Plus @@ Select[Range[Floor[n/2]], GCD[ #, n] == 1 &]; f2[n_] := Plus @@ Select[Range[Ceiling[n/2], n], GCD[ #, n] == 1 &]; Table[LCM[f1[n], f2[n]], {n, 51}] (* Ray Chandler, Nov 12 2006 *)

CROSSREFS

Cf. A066840, A124440, A124446.

Sequence in context: A132421 A132500 A129411 * A250181 A024765 A282340

Adjacent sequences: A124444 A124445 A124446 * A124448 A124449 A124450

KEYWORD

nonn

AUTHOR

Leroy Quet, Nov 01 2006

EXTENSIONS

Extended by Ray Chandler, Nov 12 2006

STATUS

approved