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A143958 Integers n > 1 such that n-1 is divisible by the difference between the largest and smallest primes dividing n. 4
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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

LINKS

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

EXAMPLE

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.

MAPLE

filter:= proc(n) local F;

  F:= [min, max](numtheory:-factorset(n));

  F[1]<F[2] and (n-1 mod (F[2]-F[1]) = 0)

end proc:

select(filter, [$2..1000]); # 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 *)

CROSSREFS

Cf. A143957.

Sequence in context: A324456 A324857 A279550 * A294278 A297366 A325472

Adjacent sequences:  A143955 A143956 A143957 * A143959 A143960 A143961

KEYWORD

nonn

AUTHOR

Leroy Quet, Sep 05 2008

EXTENSIONS

Extended by Ray Chandler, Nov 07 2008

Name edited by Jon E. Schoenfield, Nov 27 2017

STATUS

approved

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Last modified May 31 18:16 EDT 2020. Contains 334748 sequences. (Running on oeis4.)