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A072614 a(n) = Sum_{k = 1..n} (-1)^(n reduced mod k). 0
1, 2, 1, 2, 1, 4, -1, 4, 1, 4, -1, 6, -3, 8, -1, 4, -1, 8, -5, 10, -3, 8, -5, 10, -5, 10, -3, 8, -5, 14, -11, 14, -7, 12, -5, 12, -9, 14, -7, 12, -9, 18, -15, 20, -9, 14, -11, 16, -11, 18, -11, 16, -13, 22, -15, 20, -13, 18, -15, 24, -21, 26, -15, 18, -11, 20, -17, 22, -15, 24, -21, 28, -25, 30, -19, 24, -17, 26, -23, 28, -19, 24 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

FORMULA

Lim_{n -> infinity} abs(a(n))/n = C = 0.30684(3)....

MATHEMATICA

Table[ Sum[(-1)^ Mod[n, k], {k, 1, n}], {n, 1, 81} ]

PROG

(PARI) a(n)=sum(k=1, n, (-1)^(n%k))

CROSSREFS

Sequence in context: A164799 A274451 A193787 * A287597 A238552 A257523

Adjacent sequences:  A072611 A072612 A072613 * A072615 A072616 A072617

KEYWORD

sign,changed

AUTHOR

Benoit Cloitre, Aug 10 2002

STATUS

approved

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Last modified September 24 22:46 EDT 2021. Contains 347651 sequences. (Running on oeis4.)