%I A129619
%S A129619 1,1,1,3,1,1,12,16,1,17,31,31,25,1,52,52,52,61,47,23,91,102,102,114,114,
%T A129619 127,1,103,169,184,184,200,1,1,251,269,115,1,326,346,1,155,409,431,1,1,
%U A129619 1,143,525,550,1,1,602,629,101,37,463,1,753,783,783,814,89,585,910,943
%N A129619 a(n) = largest proper divisor of the sum of all positive integers which 
               are <= n and are not included among the first n-1 terms of the sequence.
%H A129619 Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> 
               (listed in lieu of email address)
%e A129619 The positive integers which are <= 8 and do not occur among the first 
               7 terms of the sequence are 2,4,5,6,7,8. a(8) is the largest proper 
               divisor of the sum of these integers. 2+4+5+6+7+8 = 32. So a(8) is 
               the largest proper divisor of 32, which is 16.
%t A129619 a = {1}; For[n = 2, n < 70, n++, AppendTo[a, Divisors[n*(n + 1)/2 - Plus 
               @@ Select[Union[a, a], # < n + 1 &]][[ -2]]]]; a - Stefan Steinerberger 
               (stefan.steinerberger(AT)gmail.com), Nov 21 2007
%Y A129619 Sequence in context: A078122 A128592 A156584 this_sequence A094573 A055154 
               A015112
%Y A129619 Adjacent sequences: A129616 A129617 A129618 this_sequence A129620 A129621 
               A129622
%K A129619 nonn
%O A129619 1,4
%A A129619 Leroy Quet May 30 2007
%E A129619 More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), 
               Nov 21 2007