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A193814
Least k such that n! + k + 1 is a prime.
0
0, 0, 0, 0, 4, 6, 6, 10, 22, 16, 10, 0, 28, 66, 18, 42, 22, 30, 36, 88, 28, 30, 30, 96, 130, 40, 58, 0, 66, 222, 106, 126, 78, 36, 96, 60, 130, 0, 42, 96, 52, 0, 96, 70, 46, 238, 100, 232, 52, 82, 60, 270, 52, 70, 222, 70, 148, 106, 282, 292, 270, 768, 130, 270, 66
OFFSET
0,5
FORMULA
a(n) = 0 for n in A002981. - Michel Marcus, Oct 10 2019
EXAMPLE
a(5) = 6 because 5! + 6 + 1 = 127 is prime.
MATHEMATICA
a={}; Do[k = 0; While[ !PrimeQ[n! + k + 1], k++ ]; AppendTo[a, k], {n, 0, 70} ]; a
ld[n_]:=Module[{f=n!}, NextPrime[f]-f-1]; Array[ld, 70, 0] (* Harvey P. Dale, Jul 13 2014 *)
PROG
(PARI) a(n) = my(k=0); while (!isprime(n!+k+1), k++); k; \\ Michel Marcus, Oct 10 2019
CROSSREFS
Sequence in context: A267573 A345282 A369749 * A304409 A081732 A079033
KEYWORD
nonn
AUTHOR
Michel Lagneau, Aug 06 2011
STATUS
approved