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A057217 a(n) = smallest positive integer k such that 1+n*k! is a prime. 1
1, 1, 2, 1, 2, 1, 3, 2, 2, 1, 2, 1, 3, 2, 2, 1, 3, 1, 4, 2, 2, 1, 2, 4, 3, 2, 3, 1, 2, 1, 7, 3, 2, 6, 2, 1, 3, 3, 2, 1, 2, 1, 4, 2, 3, 1, 3, 2, 5, 2, 2, 1, 2, 2, 3, 2, 5, 1, 11, 1, 3, 3, 2, 5, 2, 1, 4, 2, 2, 1, 5, 1, 3, 2, 2, 3, 3, 1, 14, 5, 2, 1, 2, 4, 7, 2, 3, 1, 2, 2, 3, 8, 5, 7, 2, 1, 11, 2, 2, 1, 3, 1, 3 (list; graph; refs; listen; history; internal format)
OFFSET

0,3

FORMULA

a(n)=Min{k|1+nk! is prime}

EXAMPLE

n=7, 1+7.k!={8,15,43,169,...}. The smallest k which gives prime is 3 and the prime so obtained is 43. n=267, the smallest k! is 31! for which 1+267*k! is prime and the prime so obtained is 65782709233423382541804503040000001

CROSSREFS

Sequence in context: A059829 A076558 A204893 * A193330 A147810 A055181

Adjacent sequences:  A057214 A057215 A057216 * A057218 A057219 A057220

KEYWORD

nonn

AUTHOR

Labos E. (labos(AT)ana.sote.hu), Sep 27 2000

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Last modified February 15 17:13 EST 2012. Contains 205828 sequences.