A143958 Integers n > 1 such that n-1 is divisible by the difference between the largest and smallest primes dividing n.

6, 10, 12, 15, 18, 21, 24, 33, 35, 36, 40, 45, 48, 54, 55, 56, 65, 72, 75, 77, 78, 85, 91, 96, 100, 105, 108, 126, 133, 135, 136, 143, 144, 145, 154, 160, 161, 162, 175, 187, 189, 192, 196, 209, 216, 217, 221, 225, 245, 247, 250, 253, 261, 288, 297, 323, 324, 336

Offset: 1

Author

Leroy Quet, Sep 05 2008

Keywords

• nonn

Comments

If p is prime, (p+t)*p is in the sequence if t is a divisor of p^2-1 such that p+t is prime. - Robert Israel, Nov 27 2017

Examples

			The largest prime dividing 21 is 7. The smallest prime dividing 21 is 3. 7-3 = 4 divides 21-1 = 20. So 21 is in the sequence.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A143957.

Programs

Maple

filter:= proc(n) local F;
  F:= [min,max](numtheory:-factorset(n));
  F[1]Robert Israel, Nov 27 2017

Mathematica

Select[Range[2, 336], Function[n, If[# == 0, False, Divisible[n - 1, #]] &[Last@ # - First@ #] &[FactorInteger[n][[All, 1]] ] ] ] (* Michael De Vlieger, Nov 27 2017 *)

Extensions

Extended by Ray Chandler, Nov 07 2008

Name edited by Jon E. Schoenfield, Nov 27 2017