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A093154
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Primes resulting from serial multiplication of even composites, plus 1.
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2
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5, 193, 23041, 92897281, 980995276801, 23310331287699456001, 31888533201572855808001, 13532215908553332190020108288000001, 8829205774994708066835865418197893120000001
(list; graph; refs; listen; history; internal format)
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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 plus 1 equals a prime
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EXAMPLE
| a(1) = 5 = 2*2!+1
a(2) = 193 = 2^3*4!+1
a(3) = 23041 = 2^5*6!+1
a(4) = 92897281 = 2^8*9!+1
a(5) = 980995276801 = 2^11*12!+1
a(6) = 23310331287699456001 = 2^16*17!+1
a(11) = 2^87*88!+1 is too large to include.
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CROSSREFS
| Cf. A093155.
Sequence in context: A100760 A198482 A198523 * A194572 A068793 A194573
Adjacent sequences: A093151 A093152 A093153 * A093155 A093156 A093157
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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 and extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Mar 27 2004
a(12) = 2^118*119!+1, a(13) = 2^142*143!+1. I conjecture that a(13) is the last prime number of this form. - Jorge Coveiro (jorgecoveiro(AT)yahoo.com), Apr 01 2004
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