A057155 Denominator of Sum_{k<=n} P(k)/p(k), where p(k) (resp. P(k)) is smallest (resp. largest) prime divisor of k.

1, 1, 1, 1, 1, 2, 2, 2, 2, 1, 1, 2, 2, 1, 3, 3, 3, 6, 6, 3, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 2, 6, 3, 15, 30, 30, 15, 5, 10, 10, 5, 5, 10, 30, 15, 15, 30, 30, 15, 15, 30, 30, 15, 15, 30, 30, 15, 15, 30, 30, 15, 5, 5, 5, 10, 10, 5, 15, 30, 30, 15, 15, 30, 30, 15

Offset

1,6

References

Handbook of Number Theory, D. S. Mitrinovic et al., Kluwer, Section IV.1(2).

Links

Table of n, a(n) for n=1..76.

Example

Sequence begins 1, 2, 3, 4, 5, 13/2, 15/2, 17/2, 19/2, 12, 13, 29/2, ...

Prog

(PARI) a(n) = denominator(sum(k=1, n, f = factor(k)[, 1]; if (#f, vecmax(f)/vecmin(f), 1))); \\ Michel Marcus, Feb 19 2016

Crossrefs

Cf. A057158, A020639, A006530.

Sequence in context: A104638 A270648 A331034 * A037812 A037200 A263992

Adjacent sequences: A057152 A057153 A057154 * A057156 A057157 A057158

Keyword

nonn,frac,easy

Author

N. J. A. Sloane, Sep 13 2000

Extensions

Name corrected by Michel Marcus, Feb 19 2016

Status

approved