A070890 - OEIS

A070890

Numerator of Sum_{k=1..n} mu(k)/k when it changes sign.

-1, 2, -1, 19, -1, 304, -81988, 410857, -249979, 4165258, -65721449, 2562470143, -5468849774, 184344882947, -137190436674212, 10026981687881, -12611493192339623, 519973962150962777, -8549627883788520181, 1874648830674470878723, -200643437220052588790575, 877316785444551755504875

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..22.

EXAMPLE

a(1)= -1 because numerator first sign change is 1-1/2-1/3-1/5= > (-1)/30 <0.

a(2)= 2 because next sign change is -1/30+1/6 = 2/15, reverts to positive.

PROG

(PARI) t = 0; v = []; for( n = 1, 120, t1 = t; t = t + moebius(n) / n; if( t * t1 < 0, v = concat( v, numerator( t)), )); v

CROSSREFS

Cf. A070891, A070888, A070889.