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

1,2

Comments

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

Links

Table of n, a(n) for n=1..31.

Formula

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

Example

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

Mathematica

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

Crossrefs

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

Sequence in context: A370925 A085590 A079538 * A343101 A334519 A009214

Adjacent sequences: A098218 A098219 A098220 * A098222 A098223 A098224

Keyword

nonn,more

Author

Labos Elemer, Oct 25 2004

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

Status

approved