A117004 a(n) = sigma(n) - A079667(n).

1, 2, 2, 4, 2, 6, 2, 6, 5, 6, 2, 12, 2, 6, 8, 10, 2, 12, 2, 14, 8, 6, 2, 20, 7, 6, 8, 14, 2, 22, 2, 14, 8, 6, 12, 26, 2, 6, 8, 24, 2, 24, 2, 14, 18, 6, 2, 32, 9, 16, 8, 14, 2, 24, 12, 28, 8, 6, 2, 42, 2, 6, 22, 22, 12, 24, 2, 14, 8, 30, 2, 48, 2, 6, 18, 14, 16, 24, 2, 40, 17, 6, 2, 46, 12, 6, 8, 30

Offset: 1

Author

N. J. A. Sloane, Apr 15 2006

Keywords

• nonn

References

• H. J. S. Smith, Report on the Theory of Numbers, reprinted in Vol. 1 of his Collected Math. Papers, Chelsea, NY, 1979, see p. 322.

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A079667.

Programs

Mathematica

Table[Total[Min[#,n/#]&/@Divisors[n]],{n,90}] (* Harvey P. Dale, Jan 01 2020 *)

PARI

{a(n) = sumdiv(n, d, min(d, n/d))} \\ Seiichi Manyama, Dec 27 2017

Formula

G.f.: sum(n>=1, n*x^(n^2)*(1+x^n)/(1-x^n) ). [Joerg Arndt, Jan 30 2011]

a(n) = Sum_{d|n} min(d, n/d). - Seiichi Manyama, Dec 27 2017