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 A180325 a(n) = k is the smallest number such that n is the number of distinct primes dividing k! + 1. 0
 1, 6, 9, 31, 16, 18, 40, 89 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A greedy inverse to A066856. - R. J. Mathar, Jan 21 2011 LINKS EXAMPLE a(6) = 18 because the 6 distinct primes dividing 18! + 1 = 6402373705728001   are {19, 23, 29, 61, 67, 123610951}. MAPLE with(numtheory):for n from 1 to 7 do:ind:=0:for k from 1 to 50 while(ind=0)   do: x:=k!+1:y:=nops(factorset(x)):if y=n then ind:=1:printf(`%d, `, k):else fi:od:   od: CROSSREFS Cf. A038507. Sequence in context: A086491 A178597 A179908 * A192425 A219687 A147415 Adjacent sequences:  A180322 A180323 A180324 * A180326 A180327 A180328 KEYWORD nonn,hard AUTHOR Michel Lagneau, Jan 18 2011 STATUS approved

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Last modified April 21 17:36 EDT 2021. Contains 343156 sequences. (Running on oeis4.)