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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A179402 Numbers n such that all x^4 mod n are nonprimes. 1
 1, 2, 3, 4, 5, 8, 12, 15, 16, 24, 28, 30, 40, 48, 56, 60, 72, 80, 85, 88, 96, 104, 105, 112, 120, 140, 145, 160, 168, 232, 240, 255, 265, 280, 312, 408, 420, 520, 624, 680, 760, 840, 1040, 1320, 1360, 1848, 1904, 4080 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A065428 is a subsequence. No more such numbers up to 10^6. Observe that many of these numbers are of the form k^2-1. Why? LINKS Table of n, a(n) for n=1..48. PROG (PARI) for(n=1, 10^6, q=1; for(x=1, n-1, if(isprime(component(Mod(x, n)^4, 2)), q=0; break())); if(q, print1(n, ", "))); (PARI) {a(n) = my(c, m); if(n<=1, n==1, c=1; m=1; while( c

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 18 19:41 EDT 2024. Contains 376002 sequences. (Running on oeis4.)