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A227912 Sum of all k from {1,...,n} such that the fractional part of n/k is contained in the closed interval [1/4, 3/4]. 1
0, 0, 2, 3, 9, 4, 14, 14, 19, 28, 24, 29, 41, 51, 54, 49, 67, 74, 89, 87, 99, 110, 120, 125, 142, 154, 169, 178, 180, 211, 197, 223, 262, 261, 285, 270, 299, 323, 342, 371, 359, 374, 422, 434, 477, 454, 478, 493, 538, 566, 555, 628, 606, 663, 666, 676, 716 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

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

EXAMPLE

a(6) = 4, only k = 4 satisfies the condition frac(6/k) is an element of [1/4, 3/4].

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. A227913.

Sequence in context: A242812 A089206 A249824 * A229212 A210586 A202017

Adjacent sequences:  A227909 A227910 A227911 * A227913 A227914 A227915

KEYWORD

nonn

AUTHOR

Jon Perry, Oct 13 2013

STATUS

approved

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Last modified October 16 12:00 EDT 2019. Contains 328056 sequences. (Running on oeis4.)