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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, 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 (list; graph; refs; listen; history; text; internal format)
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: A112505 A104638 A270648 * 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

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Last modified August 18 20:02 EDT 2019. Contains 326109 sequences. (Running on oeis4.)