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

1,3

Comments

Absolute first difference of A084127.

Links

Table of n, a(n) for n=1..75.

Example

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.

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 *)

Crossrefs

Cf. A001358, A006530, A084127.

Sequence in context: A008363 A261611 A097198 * A032600 A103260 A060824

Adjacent sequences: A126660 A126661 A126662 * A126664 A126665 A126666

Keyword

easy,nonn

Author

Giovanni Teofilatto, Mar 23 2007

Extensions

Edited and extended by Ray Chandler, Mar 25 2007

Status

approved