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%I #24 Oct 13 2015 12:36:08
%S 8,3,4,1410,6,154770,5246010,2894220,407874180,214580145780,
%T 9448481062020,247236503934420,2545206711847800,18178612369988250180,
%U 53792264108455702830
%N Least k such that x*k - 1 produces primes for x=1..n and composite for x=n+1.
%D Wacław Sierpiński, Czym sie zajmuje teoria liczb. Warsaw: PW "Wiedza Powszechna", 1957, pp. 88-89.
%t Table[k = 3; While[i = 1; While[i <= n && PrimeQ[i*k - 1], i++]; i <= n || PrimeQ[i*k - 1], k++]; k, {n, 8}]
%Y Another version of A088651.
%K more,nonn
%O 1,1
%A _Arkadiusz Wesolowski_, Jan 06 2012