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a(1) = 1, a(m+1) = Sum_{k=1..m} lcm(m, a(k)).
3

%I #12 Dec 12 2017 00:51:10

%S 1,1,4,18,48,360,450,6174,27000,34200,93250,1776566,11293824,

%T 172014648,1296688778,20393895570,173895132784,3328106382492,

%U 11622794050422,287786755919610,709366149217940,17019652496034468,198351459813601270

%N a(1) = 1, a(m+1) = Sum_{k=1..m} lcm(m, a(k)).

%H Michael De Vlieger, <a href="/A056147/b056147.txt">Table of n, a(n) for n = 1..506</a>

%e a(5) = lcm(4,1) + lcm(4,1) + lcm(4,4) + lcm(4,18) = 4 + 4 + 4 + 36 = 48.

%t Fold[Append[#1, Total@ LCM[#2, #1[[Range@ #2]] ] ] &, {1}, Range@ 22] (* _Michael De Vlieger_, Dec 11 2017 *)

%K easy,nonn

%O 1,3

%A _Leroy Quet_, Aug 04 2000