A072542 - OEIS

%I #3 Feb 11 2014 19:05:29

%S 2,4,6,10,12,18,20,24,30,36,48,60,60,60,72,84,96,108,120,120,144,168,

%T 168,180,180,210,240,240,240,288,288,300,336,336,360,360,360,420,420,

%U 420,480,480,504,540,600,600,600,660,660,720,720,720,720,840,840,840

%N a(n) = the least positive integer k such that sigma(k) > sigma(1) + ... + sigma(n).

%e sigma(1) + ... + sigma(4) = 15 and k = 10 is the least positive integer such that sigma(k) > 15. Hence a(4) = 10.

%t s = 0; a = {}; For[i = 1, i <= 100, i++, s = s + DivisorSigma[1, i]; k = 1; While[DivisorSigma[1, k] <= s, k = k + 1]; a = Append[a, k]]; a

%K nonn

%O 1,1

%A _Joseph L. Pe_, Dec 08 2002