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 #21 Feb 27 2020 05:57:17
%S 1,2,8,6,40,30,24,60,120,480,540,1560,2520,10920,27720,30240,191520,
%T 524160,360360,3243240,5765760,28828800,109549440,438197760,766846080,
%U 3834230400,9081072000,32974381440,147516969600,880887047040,2802822422400
%N a(n) is the smallest number x such that floor(sigma(sigma(x))/x) = n or the A098219(x) quotient equals n.
%C a(30) <= 880887047040. a(31) <= 2802822422400. - _Donovan Johnson_, Feb 16 2013
%F a(n) = Min{x;floor(A051027(x)/x)=n)
%e n = 10: a(10) = 480 because floor(sigma(sigma(480))/480) = floor(sigma(1512)/480) = floor(4800/480) = 4800/480 = n = 10.
%t t=Table[0, {100}];Do[s=g[n];If[s<101&&t[[s]]==0, t[[s]]=n], {n, 1, 1000000}];t
%Y Cf. A000203, A051027, A008333, A019278, A098219, A098220, A098222, A327630.
%K nonn,more
%O 1,2
%A _Labos Elemer_, Oct 25 2004
%E a(20)-a(26) from _Donovan Johnson_, Dec 29 2008
%E a(27)-a(29) from _Donovan Johnson_, Feb 16 2013
%E a(30)-a(31) from _Giovanni Resta_, Feb 27 2020