login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A080062 Composite numbers n such that for all primes p dividing n, p-1 divides n-1. 4
4, 8, 9, 16, 25, 27, 32, 45, 49, 64, 81, 121, 125, 128, 169, 225, 243, 256, 289, 325, 343, 361, 405, 512, 529, 561, 625, 637, 729, 841, 891, 961, 1024, 1105, 1125, 1225, 1331, 1369, 1377, 1681, 1729, 1849, 2025, 2048, 2187, 2197, 2209, 2401, 2465, 2809, 2821 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The subsequence of squarefree terms gives the Carmichael numbers (A002997); cf. Korselt's criterion. - Joerg Arndt, May 17 2016
LINKS
MATHEMATICA
Select[ Range[2, 10^4], !PrimeQ[ # ] && Union[ Mod[ # - 1, Transpose[ FactorInteger[ # ]][[1]] - 1]] == {0} &]
PROG
(PARI) is080062(n)=if(isprime(n), return(0)); my(f=factor(n)[, 1]); for(j=1, #f, if((n-1)%(f[j]-1), return(0))); 1; \\ Joerg Arndt, May 17 2016
CROSSREFS
Cf. A002997 (Carmichael numbers).
Sequence in context: A052054 A046447 A087244 * A249125 A306531 A363722
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Jan 23 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 14 13:17 EDT 2024. Contains 371661 sequences. (Running on oeis4.)