A061069 Number of distinct values in the list of divisor-sums {sigma(j) : j=1...n}.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10, 11, 12, 13, 13, 14, 14, 15, 16, 17, 18, 19, 19, 20, 20, 20, 21, 22, 23, 24, 24, 25, 26, 27, 27, 28, 29, 29, 29, 30, 30, 31, 32, 33, 34, 34, 34, 35, 36, 37, 37, 38, 38, 39, 39, 39, 40, 40, 40, 41, 42, 42, 43, 44, 44, 45, 46, 47, 47, 47, 47, 48

Offset: 1

Author

Labos Elemer, May 28 2001

Keywords

• nonn

Links

• T. D. Noe, Table of n, a(n) for n=1..1000

Crossrefs

Cf. A000203.

Programs

Python

from sympy import divisor_sigma
def A061069(n): return len({divisor_sigma(i) for i in range(1,n+1)}) # Chai Wah Wu, Sep 08 2023

Formula

a(n)=Length[Union[Table[DivisorSigma[1, w], {w, 1, n}]]]