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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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7, 47, 383, 10321919, 51011754393599, 1130138339199322632554990773529330319359999999, 73562883979319395645666688474019139929848516028923903999999999, 4208832729023498248022825567687608993477547383960134557368319999999999
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OFFSET
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1,1
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COMMENTS
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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, Mar 27 2004
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LINKS
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FORMULA
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Starting with 2, multiply even numbers until the product, minus 1, equals a prime.
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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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PROG
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CROSSREFS
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Cf. A117141 (primes of the form n!! - 1).
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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