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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A079543 Numbers n such that n has at least two distinct prime factors and if a prime p divides n then (p-1) | (n-1) and (p+1) | (n+1). 2
 74431, 71528191, 125780831, 178708831, 4150390625, 68738591551, 171739186591, 429079903231, 634061169071 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..9. Donovan Johnson, 1384 terms > a(9) EXAMPLE a(1) = 74431 = 7^4 * 31 because 6 and 30 divide 74430 and 8 and 32 divide 74432. MATHEMATICA Do[ f = Transpose[ FactorInteger[n]][[1]]; If[ Length[f] > 1 && Union[ Mod[n - 1, f - 1]] == {0} && Union[ Mod[n + 1, f + 1]] == {0}, Print[n]], {n, 6, 10^10}] CROSSREFS Intersection of A056729 and A080062. Sequence in context: A186835 A239587 A122065 * A033450 A033448 A234725 Adjacent sequences: A079540 A079541 A079542 * A079544 A079545 A079546 KEYWORD nonn AUTHOR Don Reble, Jan 22 2003 EXTENSIONS a(6)-a(7) from Donovan Johnson, Apr 09 2010 a(8)-a(9) from Donovan Johnson, Jan 21 2013 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.

Last modified August 12 17:00 EDT 2024. Contains 375113 sequences. (Running on oeis4.)