A098222 a(n) is the smallest prime q such that floor(sigma(sigma(q))/q) = n.

13, 2, 179, 55439, 232792559, 130429015516799

Offset

1,1

Comments

a(7) <= 9854961523502269526351999. If a(7) + 1 is in A025487 then a(7) = 9854961523502269526351999. a(3) + 1 through a(6) + 1 are in A025487. - David A. Corneth, Sep 03 2019

Links

Table of n, a(n) for n=1..6.

Formula

a(n) >= A091439(n). - David A. Corneth, Sep 03 2019

Example

a(4) = 55439 because floor(sigma(sigma(55439))/55439) = floor(232128/55439) = n = 4.
a(5) = 232792559 because floor(sigma(sigma(a(5)))/a(5)) = floor(5.02561) = 5.

Crossrefs

Cf. A000203, A051027, A008333, A025487, A091439, A098219, A098220, A098221.

Sequence in context: A078421 A185808 A178548 * A114457 A010220 A104818

Adjacent sequences: A098219 A098220 A098221 * A098223 A098224 A098225

Keyword

nonn,more

Author

Labos Elemer, Oct 25 2004

Extensions

a(6) from Charles R Greathouse IV, Mar 14 2011

Status

approved