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A202778
Least k such that x*k + 1 produces primes for x = 1..n and composite for x = n + 1.
0
4, 1, 2, 330, 10830, 25410, 8224860, 512820, 12960606120, 434491727670, 1893245380950, 71023095613470, 878232256181280, 11429352906540438870
OFFSET
1,1
REFERENCES
Wacław Sierpiński, Czym sie zajmuje teoria liczb. Warsaw: PW "Wiedza Powszechna", 1957, pp. 88-89.
MATHEMATICA
Table[k = 1; While[i = 1; While[i <= n && PrimeQ[i*k + 1], i++]; i <= n || PrimeQ[i*k + 1], k++]; k, {n, 8}]
CROSSREFS
Another version of A088250.
Sequence in context: A004161 A303141 A246070 * A025016 A355499 A094244
KEYWORD
more,nonn
AUTHOR
EXTENSIONS
a(14) from Giovanni Resta, Mar 31 2017
STATUS
approved