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A227913 Sum of all k from {1,...,n} such that the fractional part of n/k is contained in the open interval (1/4, 3/4). 1
0, 0, 2, 3, 5, 4, 10, 14, 15, 20, 20, 29, 37, 43, 38, 49, 63, 66, 85, 71, 83, 102, 116, 125, 118, 146, 153, 162, 176, 179, 193, 223, 246, 253, 233, 254, 295, 315, 326, 339, 355, 342, 418, 418, 405, 446, 474, 493, 506, 518, 539, 612, 602, 631, 598, 644, 700 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Differs from A227912 because the inequalities are strict.

LINKS

Table of n, a(n) for n=1..57.

EXAMPLE

a(5)=5, the valid k such that frac(5/k) is an element of (1/4,3/4) are 2 and 3, 2+3=5.

PROG

(JavaScript)

for (i=1; i<50; i++) {

c=0;

for (j=1; j<=i; j++) {

v=Math.floor(i/j);

if (i/j-v>0.25 && i/j-v<0.75) c+=j;

}

document.write(c+", ");

;

}

CROSSREFS

Cf. A227912.

Sequence in context: A246841 A066417 A254669 * A079521 A325549 A112060

Adjacent sequences:  A227910 A227911 A227912 * A227914 A227915 A227916

KEYWORD

nonn

AUTHOR

Jon Perry, Oct 13 2013

STATUS

approved

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Last modified October 14 11:55 EDT 2019. Contains 327999 sequences. (Running on oeis4.)