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Search: id:A093173
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| A093173 |
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Primes of the form (2^n * n!) - 1. |
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+0
4
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| 7, 47, 383, 10321919, 51011754393599, 1130138339199322632554990773529330319359999999, 73562883979319395645666688474019139929848516028923903999999999
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Primes resulting from serial multiplication of even numbers, minus 1.
For primes of the form 2^n*n!+1, trivially a(1)=3, a(2)=2^259*259!+1 (593 digits). - Ray Chandler (rayjchandler(AT)sbcglobal.net), Mar 27 2004
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FORMULA
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Starting with 2, multiply even numbers until the product, minus 1, equals a prime.
a(n) = A117141(n+1). - Alexander Adamchuk (alex(AT)kolmogorov.com), Apr 18 2007
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EXAMPLE
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a(1) multiplies the first 2 terms, 2*4-1. a(3) multiplies first 4 terms, a(4) multiplies first 8 terms, a(5) multiplies first 13 terms in 12 multiplications.
a(2)=47, formed by 2*4*6-1=47
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MATHEMATICA
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lst={}; Do[If[PrimeQ[p=(2^n*n!)-1], AppendTo[lst, p]], {n, 5!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Jan 28 2009]
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CROSSREFS
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Cf. A093154 A093155.
Cf. A117141 = primes of the form n!!-1.
Sequence in context: A001711 A088057 A108434 this_sequence A006873 A015097 A013400
Adjacent sequences: A093170 A093171 A093172 this_sequence A093174 A093175 A093176
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KEYWORD
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easy,nonn
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AUTHOR
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Enoch Haga (Enokh(AT)comcast.net), Mar 27 2004
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EXTENSIONS
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More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Mar 27 2004
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