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A057158 Numerator of Sum_{k<=n} P(k)/p(k), where p(k) (resp. P(k)) is smallest (resp. largest) prime divisor of k. 1
1, 2, 3, 4, 5, 13, 15, 17, 19, 12, 13, 29, 31, 19, 62, 65, 68, 145, 151, 83, 30, 71, 73, 38, 39, 91, 93, 50, 51, 107, 109, 111, 355, 203, 1036, 2117, 2147, 1216, 427, 879, 889, 462, 467, 989, 3017, 1681, 1696, 3437, 3467, 1771, 1856, 3907, 3937 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

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

LINKS

Table of n, a(n) for n=1..53.

EXAMPLE

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

PROG

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

CROSSREFS

Cf. A057155, A020639, A006530.

Sequence in context: A039039 A141484 A175303 * A138986 A306294 A098552

Adjacent sequences:  A057155 A057156 A057157 * A057159 A057160 A057161

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 November 16 17:04 EST 2019. Contains 329201 sequences. (Running on oeis4.)