A202779 Least k such that x*k - 1 produces primes for x=1..n and composite for x=n+1.

8, 3, 4, 1410, 6, 154770, 5246010, 2894220, 407874180, 214580145780, 9448481062020, 247236503934420, 2545206711847800, 18178612369988250180, 53792264108455702830

Offset: 1

Author

Arkadiusz Wesolowski, Jan 06 2012

Keywords

• more
• nonn

References

• Wacław Sierpiński, Czym sie zajmuje teoria liczb. Warsaw: PW "Wiedza Powszechna", 1957, pp. 88-89.

Crossrefs

Another version of A088651.

Programs

Mathematica

Table[k = 3; While[i = 1; While[i <= n && PrimeQ[i*k - 1], i++]; i <= n || PrimeQ[i*k - 1], k++]; k, {n, 8}]