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

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A080666 Numbers n such that n^2 + 1 and n^2 - 1 are squareful. 0
7, 41, 43, 57, 82, 93, 99, 107, 117, 118, 143, 157, 168, 193, 207, 239, 243, 251, 257, 293, 307, 327, 332, 343, 357, 368, 393, 407, 437, 443, 457, 493, 507, 515, 532, 540, 543, 557, 568, 577, 593, 606, 607, 643, 657, 693, 707, 743, 746, 757, 775, 776, 782 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This sequence is infinite. For instance, it contains all numbers of the form 100*m + 7. - Emmanuel Vantieghem, Oct 25 2016

LINKS

Table of n, a(n) for n=1..53.

MATHEMATICA

<< NumberTheory`NumberTheoryFunctions` Select[Range[10^3], ! SquareFreeQ[ #^2 - 1] && ! SquareFreeQ[ #^2 + 1] &]

PROG

(MAGMA) [n : n in [2..800] | not IsSquarefree(n^2-1) and not IsSquarefree(n^2+1)]; // Vincenzo Librandi, Oct 26 2016

CROSSREFS

Cf. A013929.

Sequence in context: A144421 A023251 A073501 * A224718 A272387 A105902

Adjacent sequences:  A080663 A080664 A080665 * A080667 A080668 A080669

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Mar 02 2003

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 January 19 06:37 EST 2020. Contains 331033 sequences. (Running on oeis4.)