A351382 Products of four distinct primes between sphenic numbers (products of 3 distinct primes).

7566, 9086, 10506, 15170, 17170, 18734, 18886, 18906, 19670, 20306, 20586, 21594, 21606, 22630, 23218, 23694, 23902, 25070, 25466, 25670, 26466, 26554, 26610, 27714, 28302, 28614, 29562, 30514, 30710, 32054, 32154, 32334, 34238, 34706, 35014, 37114, 38590, 39354

Offset: 1

Author

Massimo Kofler, Mar 28 2022

Keywords

• nonn

Comments

Numbers with at least one prime exponent greater than 1 are excluded here.

Examples

			   7566 = 2*3*13*97  (between  7565 = 5 * 17 * 89  and  7567 = 7*23*47).
   9086 = 2*7*11*59  (between  9085 = 5 * 23 * 79  and  9087 = 3*13*233).
  10506 = 2*3*17*103 (between 10505 = 5 * 11 * 191 and 10507 = 7*19*79).
  15170 = 2*5*37*41  (between 15169 = 7 * 11 * 197 and 15171 = 3*13*389).
		

Crossrefs

Cf. A007304.

Programs

Mathematica

q[n_, m_] := Module[{f = FactorInteger[n]}, Length[f] == m && Max[f[[;; , 2]]] == 1]; Select[Range[40000], q[#, 4] && q[# - 1, 3] && q[# + 1, 3] &] (* Amiram Eldar, Mar 28 2022 *)