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Search: id:A103395
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| 4, 9, 15, 21, 33, 38, 58, 65, 86, 106, 121, 129, 265, 2049, 3865, 4163, 8557, 14005, 80413, 104757, 116333, 152713, 241354, 2273893, 2492909, 16432401, 31701485, 34090613, 263504954, 424792297, 1534443805, 3233454667, 10580401481
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Intersection of A103375 with A001358.
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EXAMPLE
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14005 is an element of this sequence because A103375(106) = 14005 and
14005 is semiprime because 14005 = 5 * 2801 where both 5 and 2801 are primes. It is coincidence here that 106 = 2 * 53 is also semiprime.
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MATHEMATICA
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SemiprimeQ[n_] := Plus @@ FactorInteger[n][[All, 2]] == 2; k = 7; Do[a[n] = 1, {n, k + 1}]; a[n_] := a[n] = a[n - k] + a[n - k - 1]; Union[Select[Array[a, 255], SemiprimeQ]]
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CROSSREFS
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Cf. A001358, A103375, A103385, A103392-A103401.
Sequence in context: A103399 A103400 A103394 this_sequence A103393 A103392 A073046
Adjacent sequences: A103392 A103393 A103394 this_sequence A103396 A103397 A103398
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KEYWORD
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nonn,easy
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AUTHOR
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Jonathan Vos Post (jvospost2(AT)yahoo.com), Feb 03 2005
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EXTENSIONS
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Edited, corrected and extended by Ray Chandler (rayjchandler(AT)sbcglobal.net) and Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 06 2005
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