A105573 Numbers m such that m-4 and m+4 have 4 prime factors.

20, 136, 200, 224, 344, 346, 368, 376, 480, 488, 554, 568, 576, 640, 736, 744, 808, 816, 854, 856, 864, 872, 880, 944, 992, 1064, 1152, 1160, 1200, 1208, 1214, 1216, 1280, 1288, 1312, 1360, 1426, 1568, 1576, 1606, 1621, 1648, 1656, 1664, 1784, 1808, 1858

Offset: 1

Author

Reinhard Zumkeller, Apr 14 2005

Keywords

• nonn

Comments

A001222(a(n)-4) = A001222(a(n)+4) = 4.

Prime factors counted with multiplicity. - Harvey P. Dale, Feb 06 2020

Examples

			1214 - 4 = 1210 = 2 * 5 * 11 * 11 and 1214 + 4 = 1218 = 2 * 3 * 7 * 29 so 1214 is in the sequence. - _Jon E. Schoenfield_, Jan 19 2015
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A014574, A105571, A105572.

Programs

Mathematica

q=4;lst={};Do[If[Plus@@Last/@FactorInteger[n-q]==q&&Plus@@Last/@FactorInteger[n+q]==q,AppendTo[lst,n]],{n,7!}];lst (* Vladimir Joseph Stephan Orlovsky, Feb 01 2009 *)
Mean/@SequencePosition[PrimeOmega[Range[2000]],{4,,,_,,,_,,4}] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale, Feb 06 2020 *)