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A093173
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Primes of the form (2^n * n!) - 1.
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4
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OFFSET
| 1,1
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COMMENTS
| 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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LINKS
| Charles R Greathouse IV, Table of n, a(n) for n = 1..12
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FORMULA
| 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
| 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
| 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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PROG
| (PARI) v=[]; for(n=1, 404, if(ispseudoprime(t=n!<<n-1), v=concat(v, t))) \\ Charles R Greathouse IV, Feb 14 2011
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CROSSREFS
| Cf. A093154, A093155.
Cf. A117141 = primes of the form n!!-1.
Sequence in context: A001711 A088057 A108434 * A173772 A178002 A006873
Adjacent sequences: A093170 A093171 A093172 * A093174 A093175 A093176
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KEYWORD
| nonn
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AUTHOR
| Enoch Haga (Enokh(AT)comcast.net), Mar 27 2004
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EXTENSIONS
| More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Mar 27 2004
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