A105572 Numbers m such that m-3 and m+3 have 3 prime factors.

15, 47, 73, 95, 102, 113, 127, 150, 151, 167, 168, 185, 233, 239, 241, 258, 276, 282, 287, 289, 313, 319, 335, 360, 366, 407, 409, 415, 426, 431, 432, 433, 439, 480, 521, 527, 552, 558, 593, 599, 601, 606, 607, 612, 642, 648, 649, 654, 655, 660, 708, 713

Offset: 1

Author

Reinhard Zumkeller, Apr 14 2005

Keywords

• nonn

Comments

A001222(a(n)-3) = A001222(a(n)+3) = 3.

Prime factors counted with multiplicity. - Harvey P. Dale, May 07 2023

Examples

			From _Jon E. Schoenfield_, Jan 19 2015: (Start)
73 - 3 = 70 = 2 * 5 * 7 and 73 + 3 = 76 = 2 * 2 * 19 so 73 is in the sequence.
81 - 3 = 78 = 2 * 3 * 13 but 81 + 3 = 84 = 2 * 2 * 3 * 7 so 81 is not in the sequence. (End)
		

Links

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

Crossrefs

Cf. A014574, A105571, A105573.

Programs

Mathematica

q=3;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 *)
Flatten[Position[Partition[PrimeOmega[Range[800]],7,1],?(#[[1]]==#[[7]]==3&),1,Heads-> False]]+3 (* _Harvey P. Dale, May 07 2023 *)