Revision History for A103395
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#7 by Russ Cox at Fri Mar 30 18:40:27 EDT 2012
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| AUTHOR
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_Jonathan Vos Post (jvospost3(AT)gmail.com), _, Feb 03 2005
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Discussion
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| Fri Mar 30
| 18:40
| OEIS Server: https://oeis.org/edit/global/228
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#6 by Russ Cox at Fri Mar 30 17:31:11 EDT 2012
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| EXTENSIONS
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Edited, corrected and extended by Ray Chandler and _Robert G. Wilson v (rgwv(AT)rgwv.com), _, Feb 06 2005
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Discussion
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| Fri Mar 30
| 17:31
| OEIS Server: https://oeis.org/edit/global/156
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#5 by Russ Cox at Fri Mar 30 17:29:22 EDT 2012
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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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Discussion
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| Fri Mar 30
| 17:29
| OEIS Server: https://oeis.org/edit/global/154
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#4 by N. J. A. Sloane at Fri Jan 09 03:00:00 EST 2009
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| KEYWORD
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nonn,easy,new
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| AUTHOR
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Jonathan Vos Post (jvospost2jvospost3(AT)yahoogmail.com), Feb 03 2005
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#3 by N. J. A. Sloane at Fri Jan 12 03:00:00 EST 2007
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| KEYWORD
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nonn,easy,new
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| EXTENSIONS
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Edited, corrected and extended by Ray Chandler (RayChandlerrayjchandler(AT)alumni.tcusbcglobal.edunet) and Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 06 2005
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#2 by N. J. A. Sloane at Sat Apr 09 03:00:00 EDT 2005
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| EXAMPLE
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14005 is semiprime because 14005 = 5 x * 2801 where both 5 and 2801 are primes. It is coincidence here that 106 = 2 * 53 is also semiprime.
= 2 x 53 is also semiprime.
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| KEYWORD
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nonn,easy,new
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#1 by N. J. A. Sloane at Sun Feb 20 03:00:00 EST 2005
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| NAME
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Semiprimes in A103375.
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| DATA
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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
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| OFFSET
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1,1
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| COMMENTS
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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 x 2801 where both 5 and 2801 are primes. It is coincidence here that 106
= 2 x 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.
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| KEYWORD
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nonn,easy,new
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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 (RayChandler(AT)alumni.tcu.edu) and Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 06 2005
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| STATUS
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approved
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