Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #23 Sep 01 2017 21:28:46
%S 1,1,2,5,16,57,286,1431,9064,51398,359787,3118155,25568872,223727631,
%T 2311852188,15990310968,105935810164,1038449718056,10903722039589,
%U 185715007642033,3528585145198628,46753753173881822,658243630211230916,9215410822957232825,197209791611284782456,2112570763708981231112
%N a(1) = 1; a(n+1) = Sum_{k=1..n} a(n)/gcd(a(k),a(n)).
%H Robert Israel, <a href="/A286946/b286946.txt">Table of n, a(n) for n = 1..481</a>
%H <a href="/index/Lc#lcm">Index entries for sequences related to lcm's</a>
%F a(1) = 1; a(n+1) = Sum_{k=1..n} lcm(a(k),a(n))/a(k).
%e a(1) = 1;
%e a(2) = a(1)/gcd(a(1),a(1)) = 1/gcd(1,1) = 1;
%e a(3) = a(2)/gcd(a(1),a(2)) + a(2)/gcd(a(2),a(2)) = 1/gcd(1,1) + 1/gcd(1,1) = 2;
%e a(4) = a(3)/gcd(a(1),a(3)) + a(3)/gcd(a(2),a(3)) + a(3)/gcd(a(3),a(3)) = 2/gcd(1,2) + 2/gcd(1,2) + 2/gcd(2,2) = 5, etc.
%p A[1]:= 1:
%p for n from 1 to 50 do
%p A[n+1]:= add(A[n]/igcd(A[k],A[n]),k=1..n)
%p od:
%p seq(A[i],i=1..50); # _Robert Israel_, Sep 01 2017
%t a[1] = 1; a[n_] := a[n] = Sum[a[n - 1]/GCD[a[k - 1], a[n - 1]], {k, 2, n}]; Table[a[n], {n, 26}]
%t a[1] = 1; a[n_] := a[n] = Sum[LCM[a[k - 1], a[n - 1]]/a[k - 1], {k, 2, n}]; Table[a[n], {n, 26}]
%Y Cf. A056144, A057660, A093820, A287006.
%K nonn
%O 1,3
%A _Ilya Gutkovskiy_, Aug 31 2017