login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A338390 Numbers k such that there are exactly three biquadratefree powerful numbers (A338325) between k^2 and (k+1)^2. 6
36, 161, 364, 659, 722, 771, 896, 911, 981, 987, 1241, 1359, 1486, 1575, 1822, 2042, 2090, 2435, 2537, 2582, 2733, 2870, 2873, 2967, 2983, 3012, 3101, 3108, 3198, 3222, 3278, 3419, 3465, 3544, 3668, 3855, 3860, 3934, 4024, 4092, 4188, 4426, 4437, 4494, 4511, 4522 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Positions of 3's in A338326.

The asymptotic density of this sequence is 0.008234579... (Dehkordi, 1998).

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..6500

Massoud H. Dehkordi, Asymptotic formulae for some arithmetic functions in number theory, Ph.D. thesis, Loughborough University, 1998.

EXAMPLE

36 is a term since there are exactly three biquadratefree powerful numbers, 1323 = 3^3 * 7^2, 1331 = 11^3 and 1352 = 2^3 * 13^2, between 36^2 = 1296 and (36+1)^2 = 1369.

MATHEMATICA

bqfpowQ[n_] := AllTrue[FactorInteger[n][[;; , 2]], MemberQ[{2, 3}, #] &]; Select[Range[1000], Count[Range[#^2 + 1, (# + 1)^2 - 1], _?bqfpowQ] == 3 &]

CROSSREFS

Cf. A336178, A338325, A338326, A338327, A338387, A338388, A338389, A338391, A338392.

Sequence in context: A280397 A064500 A264474 * A268905 A017054 A231972

Adjacent sequences:  A338387 A338388 A338389 * A338391 A338392 A338393

KEYWORD

nonn

AUTHOR

Amiram Eldar, Oct 23 2020

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 July 29 11:03 EDT 2021. Contains 346344 sequences. (Running on oeis4.)