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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
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refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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EXAMPLE
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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.
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MATHEMATICA
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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 *)
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CROSSREFS
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KEYWORD
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nonn,easy,changed
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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