A098219 a(n) = floor(sigma(sigma(n))/n) = floor(A051027(n)/n).

1, 2, 2, 2, 2, 4, 2, 3, 1, 3, 2, 4, 1, 4, 4, 2, 2, 3, 2, 4, 3, 4, 2, 7, 1, 3, 3, 4, 2, 6, 2, 3, 3, 3, 3, 3, 1, 4, 3, 5, 2, 6, 1, 5, 3, 4, 2, 4, 1, 2, 3, 3, 2, 6, 3, 6, 3, 4, 2, 8, 1, 4, 3, 2, 3, 6, 1, 4, 3, 5, 2, 4, 1, 3, 2, 4, 3, 6, 2, 4, 1, 3, 2, 6, 3, 3, 4, 6, 2, 6, 2, 5, 2, 4, 3, 7, 1, 2, 3, 2, 2, 5, 2, 5, 4

Offset: 1

Author

Labos Elemer, Oct 25 2004

Keywords

• nonn

Examples

			For n=10, a(10) = floor(sigma(sigma(10))/10) = floor(sigma(18)/10) = floor(39/10) = 3.
		

Links

• Indranil Ghosh, Table of n, a(n) for n = 1..25000

Crossrefs

Cf. A000203, A051027, A008333, A098220, A098221, A098222.

Programs

Mathematica

Table[Floor[Nest[DivisorSigma[1, #] &, n, 2]/n], {n, 120}] (* Michael De Vlieger, Mar 02 2017 *)

PARI

a(n) = sigma(sigma(n))\n; \\ Michel Marcus, Oct 07 2019