A103394 Semiprimes in A103374.

4, 9, 15, 21, 33, 38, 58, 65, 86, 106, 121, 129, 265, 979, 1079, 2279, 7985, 8491, 14019, 15397, 37606, 61289, 71845, 117013, 127401, 196763, 221905, 244414, 265358, 290111, 466319, 555469, 1065241, 1672598, 4276487, 4712791, 5266246, 8178897

Offset

1,1

Links

Table of n, a(n) for n=1..38.

Example

61289 is an element of this sequence because A103374(107) = 61289 and 61289 is semiprime because 61289 = 167 * 367 where both 167 and 367 are primes.

Mathematica

SemiprimeQ[n_] := Plus @@ FactorInteger[n][[All, 2]] == 2; k = 6; Do[a[n] = 1, {n, k + 1}]; a[n_] := a[n] = a[n - k] + a[n - k - 1]; Union[Select[Array[a, 160], SemiprimeQ]]
Select[LinearRecurrence[{0, 0, 0, 0, 0, 1, 1}, {1, 1, 1, 1, 1, 1, 1}, 200], PrimeOmega[#]==2&]//Union (* Harvey P. Dale, Sep 02 2024 *)

Crossrefs

Intersection of A103374 with A001358.

Cf. A001358, A103374, A103384, A103392-A103401.

Sequence in context: A103399 A103398 A103397 * A103395 A103393 A103392

Adjacent sequences: A103391 A103392 A103393 * A103395 A103396 A103397

Keyword

nonn,easy

Author

Jonathan Vos Post, Feb 03 2005

Extensions

Edited and extended by Ray Chandler and Robert G. Wilson v, Feb 06 2005

Status

approved