A238502 Let k = A239161(n); then a(n) = (sum of divisors of k) /(sum of divisors d of k with d <= sqrt(k)).

1, 3, 4, 6, 4, 8, 5, 6, 12, 14, 8, 6, 18, 20, 6, 8, 12, 24, 6, 14, 10, 8, 30, 32, 9, 12, 18, 8, 38, 20, 14, 42, 8, 44, 12, 24, 48, 18, 14, 54, 10, 12, 20, 30, 60, 8, 62, 32, 14, 12, 68, 18, 24, 72, 74, 38, 20, 12, 14, 80, 42, 84, 18, 44, 30, 12, 90, 9, 14, 24

Offset: 1

Author

Michel Lagneau, Feb 27 2014

Keywords

• nonn

Comments

A000203(k)/A066839(k) is an integer, where k = A239161(n).

Examples

			a(10) = 14 because k = A239161(10) = 13 and A000203(13) = 14, A066839(13) = 1 and A000203(13)/A066839(13) is an integer.
		

Links

• Michel Lagneau, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A066839, A239161.

Programs

Mathematica

lst={}; f[n_]:=DivisorSigma[1,n]/Plus@@Select[Divisors@n,#<=Sqrt@n&];Do[If[IntegerQ[f[n]],AppendTo[lst, f[n]]],{n,1,200}];lst

PARI

lista(nn) = { for(n = 1, nn, q = sigma(n) / sumdiv(n, d, d*(d<=sqrt(n))); if (type(q) == "t_INT", print1(q, ", ")););} \\ Michel Marcus, Mar 05 2014