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!)
A339473 Numbers k such that floor(sqrt(k)) divides k^2, but does not divide k. 0
18, 22, 68, 76, 84, 87, 93, 96, 150, 162, 260, 264, 268, 276, 280, 284, 330, 336, 348, 354, 410, 430, 588, 612, 630, 635, 640, 645, 655, 660, 665, 670, 738, 747, 765, 774, 798, 826, 1032, 1040, 1048, 1064, 1072, 1080, 1302, 1308, 1314, 1320, 1326, 1338, 1344, 1350 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..52.

EXAMPLE

18 is in the sequence since floor(sqrt(18)) = 4, which does not divide 18, but it does divide 18^2 = 324.

MATHEMATICA

Flatten[Table[If[(1 - Ceiling[n^2/Floor[Sqrt[n]]] + Floor[n^2/Floor[Sqrt[n]]]) (Ceiling[n/Floor[Sqrt[n]]] - Floor[n/Floor[Sqrt[n]]]) == 1, n, {}], {n, 2000}]]

PROG

(PARI) isok(k) = (k % sqrtint(k)) && !(k^2 % sqrtint(k)); \\ Michel Marcus, Apr 24 2021

(Python)

from math import isqrt

def ok(k): r = isqrt(k); return k % r != 0 and k**2 % r == 0

print(list(filter(ok, range(1, 1351)))) # Michael S. Branicky, Apr 24 2021

CROSSREFS

Cf. A006446.

Sequence in context: A290172 A031407 A267826 * A002505 A182438 A050772

Adjacent sequences:  A339470 A339471 A339472 * A339474 A339475 A339476

KEYWORD

nonn

AUTHOR

Wesley Ivan Hurt, Apr 24 2021

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 August 1 05:51 EDT 2021. Contains 346384 sequences. (Running on oeis4.)