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A093155
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Primes resulting from serial multiplication of even composites, minus 1.
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3
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OFFSET
| 1,1
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COMMENTS
| Primes of the form 2^n*(n+1)!-1.
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FORMULA
| Starting with 4 multiply even composites until the product minus 1 equals a prime
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EXAMPLE
| a(1) = 3 = 2*2!-1
a(2) = 23 = 2^2*3!-1
a(3) = 191 = 2^3*4!-1
a(4) = 23039 = 2^5*6!-1
a(5) = 322559 = 2^6*7!-1
a(6) = 5160959 = 2^7*8!-1
a(7) = 40874803199 = 2^10*11!-1
a(8) = 25505877196799 = 2^12*13!-1
a(9) = 2^101*102!-1 is too large to include.
a(10) = 2^117*118!-1, a(11) = 2^227*228!-1. - Jorge Coveiro
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PROG
| (PARI) for(x=1, 500, if(isprime(2^x*(x+1)!-1), print(x))) - Jorge Coveiro (jorgecoveiro(AT)yahoo.com), Dec 24 2004
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CROSSREFS
| Cf. A093154.
Sequence in context: A144479 A074579 A060880 * A096649 A135423 A114017
Adjacent sequences: A093152 A093153 A093154 * A093156 A093157 A093158
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KEYWORD
| easy,nonn
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AUTHOR
| Enoch Haga (Enokh(AT)comcast.net), Mar 25 2004
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EXTENSIONS
| Edited by Ray Chandler (rayjchandler(AT)sbcglobal.net), Mar 27 2004
The next term is too large to include.
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