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A035093 Smallest k such that k*n! + 1 is prime. 9
1, 1, 1, 3, 2, 3, 3, 4, 3, 3, 1, 2, 3, 13, 7, 4, 5, 2, 7, 17, 15, 18, 3, 6, 3, 16, 1, 4, 7, 20, 8, 3, 9, 5, 2, 7, 1, 3, 10, 3, 1, 29, 7, 9, 45, 8, 3, 6, 35, 66, 2, 20, 2, 4, 25, 52, 14, 34, 24, 6, 10, 22, 38, 16, 20, 91, 69, 12, 19, 20, 21, 42, 1, 5, 33, 77, 1, 2, 12, 29, 193, 74, 40, 55, 19 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
COMMENTS
This is one possible generalization of "the least prime problem" for n*k+1 arithmetic progression when n is replaced by n!, a special difference.
LINKS
EXAMPLE
a(7)=3 because in progression of 5040*k+1 the terms 5041 and 10081 are not prime and so 15121 is the first prime.
MATHEMATICA
Table[k = 1; While[! PrimeQ[1 + k*n!], k++]; k, {n, 85}] (* T. D. Noe, Nov 04 2013 *)
PROG
(PARI) a(n) = my(k=1); while(!isprime(k*n!+1), k++); k; \\ Michel Marcus, Sep 26 2020
CROSSREFS
Analogous case is A034693. Special case for k=1 is A002981.
Sequence in context: A130970 A144733 A091460 * A292511 A238872 A260195
KEYWORD
nonn
AUTHOR
EXTENSIONS
a(80) corrected by Alex Ratushnyak, Nov 03 2013
Simpler title by Sean A. Irvine, Sep 25 2020
STATUS
approved

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Last modified July 12 21:16 EDT 2024. Contains 374257 sequences. (Running on oeis4.)