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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
OFFSET
1,6
REFERENCES
Handbook of Number Theory, D. S. Mitrinovic et al., Kluwer, Section IV.1(2).
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
KEYWORD
nonn,frac,easy
AUTHOR
N. J. A. Sloane, Sep 13 2000
EXTENSIONS
Name corrected by Michel Marcus, Feb 19 2016
STATUS
approved