%I #51 Feb 27 2020 05:57:22
%S 1,2,6,6,24,24,24,60,120,480,540,1560,2520,10920,27720,30240,191520,
%T 360360,360360,3243240,5765760,28828800,109549440,438197760,766846080,
%U 3834230400,9081072000,32974381440,147516969600,880887047040,2802822422400
%N a(n) is the least integer k such that sigma(sigma(k)) >= n*k where sigma is A000203, the sum of divisors.
%C From _Daniel Suteu_, Oct 10 2019: (Start)
%C a(32) <= 14814918518400,
%C a(33) <= 64464915715200,
%C a(34) <= 709114072867200,
%C a(35) <= 9881550651772800,
%C a(36) <= 76648784785372800,
%C a(37) <= 2376112328346556800. (End)
%o (PARI) a(n) = my(k=1); while (sigma(sigma(k))/k < n, k++); k;
%Y Cf. A000203, A007539, A023199, A098221, A019278.
%Y Cf. A051027, A272930.
%K nonn,more
%O 1,2
%A _Michel Marcus_, Oct 07 2019
%E a(23)-a(29) from _Giovanni Resta_, Oct 07 2019
%E a(30)-a(31) from _Giovanni Resta_, Feb 27 2020