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

13, 2, 179, 55439, 232792559, 130429015516799

Offset: 1

Author

Labos Elemer, Oct 25 2004

Keywords

• nonn
• more

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

Examples

			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.

Formula

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

Extensions

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