A126663 Absolute difference between largest prime factors of two successive semiprimes.

1, 0, 2, 2, 2, 2, 4, 6, 8, 2, 6, 10, 12, 6, 10, 16, 10, 6, 8, 10, 2, 18, 10, 14, 26, 30, 24, 26, 14, 16, 18, 16, 28, 34, 16, 14, 36, 42, 6, 50, 20, 2, 24, 48, 20, 24, 58, 16, 44, 42, 48, 26, 30, 60, 70, 46, 30, 28, 24, 20, 80, 30, 34, 72, 12, 62, 84, 52, 36, 64, 12, 78, 36, 56, 96

Offset: 1

Author

Giovanni Teofilatto, Mar 23 2007

Keywords

• easy
• nonn

Comments

Absolute first difference of A084127.

Examples

			a(1) = 1 because 4 = 2*2 and 6 = 2*3 so 3 - 2 = 1;
a(2) = 0 because 6 = 2*3 and 9 = 3*3 so 3 - 3 = 0;
a(3) = 2 because 9 = 3*3 snd 10 = 2*5 so 5 - 3 = 2.
		

Crossrefs

Cf. A001358, A006530, A084127.

Programs

Mathematica

Select[ FactorInteger[ Range[300]], Total[#[[All, 2]]] == 2 &][[All, -1, 1]] // Differences // Abs (* Jean-François Alcover, Dec 03 2013 *)
Abs[#[[1]]-#[[2]]]&/@(Partition[FactorInteger[#][[-1,1]]&/@Select[ Range[ 300],PrimeOmega[#]==2&],2,1]) (* Harvey P. Dale, Nov 07 2020 *)

Extensions

Edited and extended by Ray Chandler, Mar 25 2007