A175668 First differences of A175648.

4, 11, 1, 12, 1, 16, 7, 7, 17, 5, 4, 20, 4, 3, 1, 10, 12, 1, 13, 28, 18, 1, 3, 4, 4, 1, 1, 2, 32, 25, 13, 4, 4, 3, 1, 2, 4, 14, 4, 12, 23, 3, 16, 5, 9, 3, 9, 4, 4, 2, 34, 7, 15, 9, 3, 4, 4, 4, 4, 4, 10, 4, 14, 4, 5, 24, 17, 43, 7, 38, 14, 4, 9, 1, 4, 4, 10, 4, 28, 4, 14, 4, 14, 4, 4, 10, 4, 10

Offset

1,1

Comments

Distance between twin semiprime pairs.

Links

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

Maple

A175648 := proc(n) option remember; if n = 1 then 6; else for a from procname(n-1)+1 do if numtheory[bigomega](a) = 2 and numtheory[bigomega](a+4) = 2 then return a; end if; end do: end if; end proc:
A175668 := proc(n) A175648(n+1)-A175648(n) ; end proc:
seq(A175668(n), n=1..100) ; # R. J. Mathar, Aug 07 2010

Mathematica

Differences[SequencePosition[Table[If[PrimeOmega[n]==2, 1, 0], {n, 1000}], {1, _, _, _, 1}][[;; , 1]]] (* Harvey P. Dale, Jan 18 2026 *)

Crossrefs

Cf. A053319, A175612, A175648.

Sequence in context: A230024 A132150 A091389 * A113249 A087171 A282026

Adjacent sequences: A175665 A175666 A175667 * A175669 A175670 A175671

Keyword

nonn

Author

Juri-Stepan Gerasimov, Aug 05 2010

Extensions

Terms from a(33) on corrected by R. J. Mathar, Aug 07 2010

Status

approved