A079554 a(n) = floor( d(n) * log(n) / 2 ), where d() = A000005.

0, 0, 1, 2, 1, 3, 1, 4, 3, 4, 2, 7, 2, 5, 5, 6, 2, 8, 2, 8, 6, 6, 3, 12, 4, 6, 6, 9, 3, 13, 3, 10, 6, 7, 7, 16, 3, 7, 7, 14, 3, 14, 3, 11, 11, 7, 3, 19, 5, 11, 7, 11, 3, 15, 8, 16, 8, 8, 4, 24, 4, 8, 12, 14, 8, 16, 4, 12, 8, 16, 4, 25, 4, 8, 12, 12, 8, 17, 4, 21, 10, 8, 4, 26, 8, 8, 8, 17, 4, 26, 9, 13

Offset

1,4

References

József Sándor, Dragoslav S. Mitrinovic, and Borislav Crstici, Handbook of Number Theory I, Springer Science & Business Media, 2005, Chapter II, p. 41.

Links

Table of n, a(n) for n=1..92.

Mathematica

a[n_] := Floor[DivisorSigma[0, n] * Log[n] / 2]; Array[a, 100] (* Amiram Eldar, Apr 07 2024 *)

Prog

(PARI) a(n) = numdiv(n) * log(n) \ 2; \\ Amiram Eldar, Apr 07 2024

Crossrefs

Cf. A000005.

Sequence in context: A323906 A020952 A332294 * A247892 A366649 A079880

Adjacent sequences: A079551 A079552 A079553 * A079555 A079556 A079557

Keyword

nonn

Author

N. J. A. Sloane, Jan 24 2003

Extensions

Name corrected by Amiram Eldar, Apr 07 2024

Status

approved