A098221 a(n) is the smallest number x such that floor(sigma(sigma(x))/x) = n or the A098219(x) quotient equals n.

1, 2, 8, 6, 40, 30, 24, 60, 120, 480, 540, 1560, 2520, 10920, 27720, 30240, 191520, 524160, 360360, 3243240, 5765760, 28828800, 109549440, 438197760, 766846080, 3834230400, 9081072000, 32974381440, 147516969600, 880887047040, 2802822422400

Offset: 1

Author

Labos Elemer, Oct 25 2004

Keywords

• nonn
• more

Comments

a(30) <= 880887047040. a(31) <= 2802822422400. - Donovan Johnson, Feb 16 2013

Examples

			n = 10: a(10) = 480 because floor(sigma(sigma(480))/480) = floor(sigma(1512)/480) = floor(4800/480) = 4800/480 = n = 10.
		

Crossrefs

Cf. A000203, A051027, A008333, A019278, A098219, A098220, A098222, A327630.

Programs

Mathematica

t=Table[0, {100}];Do[s=g[n];If[s<101&&t[[s]]==0, t[[s]]=n], {n, 1, 1000000}];t

Formula

a(n) = Min{x;floor(A051027(x)/x)=n}.

Extensions

a(20)-a(26) from Donovan Johnson, Dec 29 2008

a(27)-a(29) from Donovan Johnson, Feb 16 2013

a(30)-a(31) from Giovanni Resta, Feb 27 2020