login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A278100 Number of squarefree positive integers less than n^2. 4
0, 3, 6, 11, 16, 23, 31, 39, 50, 61, 75, 89, 103, 120, 139, 157, 177, 199, 219, 243, 269, 297, 323, 351, 381, 412, 444, 477, 513, 547, 584, 624, 660, 703, 745, 789, 835, 882, 928, 977, 1025, 1073, 1124, 1174, 1230, 1285, 1342, 1400, 1460, 1523, 1582, 1645, 1708 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Jason Kimberley, Table of n, a(n) for n = 1..5000

FORMULA

a(n) = A013928(n^2).

MATHEMATICA

Table[Count[Range[n^2], k_ /; SquareFreeQ@ k], {n, 53}] (* Michael De Vlieger, Nov 24 2016 *)

PROG

(Magma)

A278100:=func<n|#[k:k in[1..n^2-1]|IsSquarefree(k)]>;

[A278100(n):n in[1..53]]; // in cubic time

(PARI) a(n) = #select(x->issquarefree(x), vector(n^2-1, k, k)); \\ Michel Marcus, Nov 12 2016

CROSSREFS

Cf. A005117, A013928.

This is the row length sequence of A277648 and A278101.

Sequence in context: A266252 A267260 A116940 * A087099 A075703 A267583

Adjacent sequences:  A278097 A278098 A278099 * A278101 A278102 A278103

KEYWORD

nonn,easy

AUTHOR

Jason Kimberley, Nov 12 2016

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 16 13:32 EDT 2019. Contains 328093 sequences. (Running on oeis4.)