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Search: id:A092108
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| A092108 |
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Numbers n such that n-th prime + n-th semiprime is prime. |
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+0
2
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| 4, 8, 12, 21, 38, 45, 47, 52, 58, 62, 70, 111, 142, 143, 155, 178, 269, 301, 348, 359, 364, 387, 395, 403, 435, 442, 451, 464, 497, 525, 529, 577, 579, 582, 585, 598, 624, 700, 709, 716, 752, 764, 797, 800, 803, 814, 836, 841, 864, 873, 877, 922, 934, 978, 990
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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12 is a member because 12-th prime is 37, 12-th semiprime is 34 and 37+34=71 is prime.
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MATHEMATICA
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PrimeFactorExponentsAdded[n_] := Plus @@ Flatten[Table[ #[[2]], {1}] & /@ FactorInteger[n]]; sp = Select[Range[ 3700], PrimeFactorExponentsAdded[ # ] == 2 &]; p = Table[Prime[i], {i, Length[sp]}]; Select[ Range[ Length[sp]], PrimeQ[ sp[[ # ]] + p[[ # ]]] &] (from Robert G. Wilson v Feb 24 2004)
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CROSSREFS
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Sequence in context: A122108 A123723 A128233 this_sequence A015781 A130643 A014617
Adjacent sequences: A092105 A092106 A092107 this_sequence A092109 A092110 A092111
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KEYWORD
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easy,nonn
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), Feb 22 2004
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com) and Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 24 2004
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