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a(n) = LCM { sigma(1), ..., sigma(n) }.
3

%I #13 Dec 11 2024 08:38:15

%S 1,1,3,12,84,84,84,168,840,10920,32760,32760,32760,32760,32760,32760,

%T 1015560,1015560,1015560,1015560,1015560,4062240,4062240,4062240,

%U 4062240,4062240,4062240,4062240,4062240,4062240,4062240,4062240,4062240,4062240,12186720

%N a(n) = LCM { sigma(1), ..., sigma(n) }.

%H Alois P. Heinz, <a href="/A051549/b051549.txt">Table of n, a(n) for n = 0..10000</a>

%p a:= proc(n) option remember; `if`(n=0, 1,

%p ilcm(a(n-1), numtheory[sigma](n)))

%p end:

%p seq(a(n), n=0..35); # _Alois P. Heinz_, Dec 11 2024

%t nn=40;With[{sig=DivisorSigma[1,Range[nn]]},Table[LCM@@Take[sig,n],{n,nn}]] (* _Harvey P. Dale_, Nov 15 2013 *)

%Y Cf. A000203.

%K nonn

%O 0,3

%A _N. J. A. Sloane_

%E a(0)=1 inserted by _Alois P. Heinz_, Dec 11 2024