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!)
A329417 Carmichael numbers m that have at least 3 prime factors p such that (p-1)*p^2 divides m-p. 3
12876480001, 102293818705, 162303632569, 639554081761, 783962120161, 3224063844001, 4553777859841, 10276904735461, 40867660260505, 51496980091921, 51641004415105, 52412615611201, 52933062609505, 73892907966241, 97388953462801, 107862864807061, 182236335107905, 210587050134721 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

In 1950, Giuga conjectured that there are no composite numbers n for which 1^(n-1) + 2^(n-1) + ... + (n-1)^(n-1) == -1 (mod n). If such a number exists, then it must be a Carmichael number n such that (p-1)*p^2 divides n-p for every prime p dividing n.

REFERENCES

Giuseppe Giuga, Su una presumibile proprietà caratteristica dei numeri primi (in Italian), Istituto Lombardo Scienze e Lettere, Rendiconti di Classe di scienze matematiche e naturali, Vol. 83 (1950), pp. 511-528.

LINKS

Daniel Suteu, Table of n, a(n) for n = 1..854 (terms below 2^64)

Takashi Agoh, On Giuga's conjecture, Manuscripta Mathematica, Vol. 87, No. 1 (1995), pp. 501-510.

William D. Banks, C. Wesley Nevans and Carl Pomerance, A remark on Giuga's conjecture and Lehmer's totient problem, Albanian Journal of Mathematics, Vol. 3, No. 2 (2009), pp. 81-85, alternative link.

Eric Weisstein's World of Mathematics, Giuga's Conjecture.

Wikipedia, Agoh-Giuga conjecture.

EXAMPLE

m = 12876480001 is a term because it is a Carmichael number, and it has at least 3 prime factors p, {7, 11, 37}, such that (p-1)*p^2 divides m-p.

PROG

(Perl) use bigint; use ntheory ':all'; sub isok { my $m = $_[0]; is_carmichael($m) && (grep { ($m-$_) % (($_-1)*$_*$_) == 0 } factor($m)) >= 3 };

CROSSREFS

Cf. A002997.

Sequence in context: A135496 A287747 A113642 * A216866 A034657 A204096

Adjacent sequences:  A329414 A329415 A329416 * A329418 A329419 A329420

KEYWORD

nonn

AUTHOR

Amiram Eldar and Daniel Suteu, Nov 29 2019

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 November 29 04:22 EST 2021. Contains 349416 sequences. (Running on oeis4.)