Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #15 Mar 04 2018 17:43:50
%S 1,1,2,2,12,2,60,2,30,2,570,2,4116,2,144,2,39600,2,747694,2,9720308,2,
%T 115638138,2,1261104380,2,3814717230,2,137331022698,2,2137994925180,2,
%U 8901006912,2,274682981784,2,46154014360092,2,29022598622,2
%N a(1)=1; a(n) = lcm((number of earlier terms which are coprime to n), (sum of the earlier terms which are coprime to n)).
%C For n > 2, a(n) is even since by induction the sum of coprimes is 1+1+some even numbers. Therefore a(n) = 2 for even n > 2 since only the 1's are coprime.
%H H. v. Eitzen, <a href="/A128269/b128269.txt">Table of n, a(n) for n = 1..1000</a>
%e Among {a(1),a(2),...a(8)} the terms which are coprime to 9 are a(1)=a(2)=1 and a(3)=a(4)=a(6)=a(8)=2. There are 6 such terms. And the sum of these terms is 10. So a(8) = lcm(6,10) = 30.
%Y Cf. A128268.
%K nonn
%O 1,3
%A _Leroy Quet_, Feb 22 2007
%E More terms copied from b-file by _Hagen von Eitzen_, Jun 24 2009