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 A125838 a(n) is the smallest number m such that k*m - 1 for k=2,3,...,n is prime. 4
 2, 2, 2, 6, 120, 120, 2894220, 397073040, 1236161850, 764907546690, 8955490023480, 138393712627170, 8047290924923250 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 LINKS Carlos Rivera, Problems & Puzzles. EXAMPLE a(7)=120 because 2*120-1, 3*120-1, 4*120-1, 5*120-1, 6*120-1 & 7*120-1 are prime and 120 is the smallest such number. MATHEMATICA a[n_] := Block[{k=2}, While[! AllTrue[k Range[2, n] - 1, PrimeQ], k += 2]; k]; a /@ Range[2, 8] (* Giovanni Resta, Mar 29 2017 *) CROSSREFS Cf. A125839, A088651, A088250. Sequence in context: A098920 A270557 A129365 * A021453 A053789 A115596 Adjacent sequences:  A125835 A125836 A125837 * A125839 A125840 A125841 KEYWORD hard,more,nonn AUTHOR Carlos Rivera, Jan 01 2007 EXTENSIONS a(8) from Luke Pebody (luke.pebody(AT)gmail.com) a(9)-a(10) from Vladimir Trushkov (vladimir(AT)trushkov.botik.ru) a(11) from Farideh Firoozbakht a(5) corrected by and a(12)-a(14) from Giovanni Resta, Mar 29 2017 STATUS approved

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Last modified May 26 19:44 EDT 2019. Contains 323597 sequences. (Running on oeis4.)