A103396 Semiprimes in A103376.

4, 9, 15, 21, 33, 38, 58, 65, 86, 106, 121, 129, 265, 511, 2038, 2059, 4097, 4174, 7894, 16021, 19857, 31313, 32419, 33238, 37711, 116197, 196609, 220937, 262978, 273926, 955743, 34826059, 64229819, 67835071, 77834009, 497049562, 4370946037

Offset

1,1

Comments

Intersection of A103376 with A001358.

Links

Table of n, a(n) for n=1..37.

Mathematica

SemiprimeQ[n_] := Plus @@ FactorInteger[n][[All, 2]] == 2; k = 8; Do[a[n] = 1, {n, k + 1}]; a[n_] := a[n] = a[n - k] + a[n - k - 1]; Union[Select[Array[a, 280], SemiprimeQ]]
Union[Select[LinearRecurrence[{0, 0, 0, 0, 0, 0, 0, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1}, 300], PrimeOmega[#]==2&]] (* Harvey P. Dale, May 07 2015 *)

Crossrefs

Cf. A001358, A103376, A103386, A103392-A103401.

Sequence in context: A099055 A162801 A335250 * A103400 A103399 A103398

Adjacent sequences: A103393 A103394 A103395 * A103397 A103398 A103399

Keyword

nonn,easy

Author

Jonathan Vos Post, Feb 05 2005

Extensions

Edited and extended by Ray Chandler, Feb 10 2005

Status

approved