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A093082
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Number of steps to factor n!-1 using Fermat's factorization method.
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2
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1, 1, 8, 2, 334, 2450, 688, 958, 60676, 151, 239478914, 1718557, 43588850341, 44525, 3435544097, 128202996855, 166046498, 468640744, 9748065626452, 2406214305714, 54782975386, 249195119225246375, 20940713346, 57388133232314021954, 9869596698791300782235, 187739128455384480612259907, 184395236716104
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OFFSET
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2,3
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LINKS
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FORMULA
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For n>2, a(n) = (d + (m)/d)/2 - floor(sqrt(m)), where m=n!-1 and d is the smallest divisor of m such that d >=sqrt(m). - Max Alekseyev, Apr 13 2009
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PROG
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(PARI) { a(n) = my(m); if(n==2, return(1)); m=n!-1; fordiv(m, d, if(d*d>=m, return((d+m\d)\2-sqrtint(m)); ); ) } /* Max Alekseyev, Apr 13 2009 */
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CROSSREFS
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KEYWORD
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hard,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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