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A241147 a(n) = the number of integers i in {1,2,...,L}, where L = lcm(1,2,...,n), having the property that the number of positive integer divisors of i that are less than or equal to n, is odd. 0
1, 1, 3, 7, 33, 33, 225, 405, 1305, 1235, 13635, 13635, 177705, 170775, 170181, 359073, 6106815, 5919705, 112887225, 109706355, 110362725, 107787735 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

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

EXAMPLE

For n = 4 we have a(n) = 7, since the divisors <=4 of 1,2,..., 12 are

{1}, {1,2}, {1,3}, {1,2,4}, {1}, {1,2,3}, {1}, {1,2,4}, {1,3}, {1,2}, {1}, and {1,2,3,4}, and only 7 of these have odd cardinality.

CROSSREFS

Sequence in context: A074699 A115088 A089622 * A143967 A007646 A238314

Adjacent sequences:  A241144 A241145 A241146 * A241148 A241149 A241150

KEYWORD

nonn

AUTHOR

Jeffrey Shallit, Apr 16 2014

STATUS

approved

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Last modified August 20 04:25 EDT 2019. Contains 326139 sequences. (Running on oeis4.)